Authors:
- Joellen Dimond, Former Extension Agent, Tennessee State University
- Carol Reese, Retired Extension Specialist, University of Tennessee
Introduction
Landscape Goals
The chapters of this manual dealing with landscape design introduced the philosophy that a landscape is much more than a collection of plants. It is an expression of personal style and philosophy. A thoughtful residential landscape accommodates each family’s needs and lifestyle. It may create new living spaces, produce food, or address needs such as access or parking. Maintenance challenges may be resolved or privacy enhanced even as beautiful habitat is created for wildlife.
Structures may be used to accomplish some of these objectives, as may woody plants. Herbaceous plants can also be players in these functional roles as components of screens or as ground covers (see page 9-6). They can provide food for a family and for wildlife, or they may be used purely for aesthetics for seasonal color, texture, or form. Best success will be obtained by taking a logical approach, first assessing the site and then choosing the appropriate plants for the desired goals.
Site Realities
The first question to ask is “What is really possible on this site?” Proper site selection is an essential requirement for the survival and performance of herbaceous plants. Environments in the planting bed are a combination of moisture, soil types, and sunlight availability. Common descriptions of planting areas include terms such as sun, shade, part shade, dry, hot, moist, boggy, and rocky. Competition with nearby trees or shrubs for water, light, and nutrients can also be an important factor. To be considered a full sun or sunny location, the site must receive at least six hours of direct sun each day (see page 9-6).
Partial shade means that the site gets at least a few hours of direct sun during the day, but the effect on plants can be very different if those hours of direct sun occur during the hottest times of the day—at midday or early afternoon —rather than in the morning or evening. Many plants that prosper with morning sun will suffer in afternoon sun.
The intensity of the shade is another factor. Some trees have a thinner canopy, allowing passage of dappled light throughout the day. In this intermittent sunlight, which may be considered light shade, many plants can thrive. On the other hand, the deep shade created by permanent structures or trees with dense canopies is challenging to most plants. If plants are to be grown in deep shade, it will be necessary to find the relatively few that tolerate the lack of plentiful light or find a way to increase the amount of light—for example, in the case of trees, by removing or thinning some branches to allow more light to pass through.
Matching Plant Materials with Landscape Goals
The term herbaceous refers to plants with fleshy, soft, or succulent stems. Some such plants will die back to the ground in winter, while others are evergreen. Some have stalks that may feel very woody (such as sunflower stalks) but lack the xylem found in true wood. Annual and perennial flowers, grasses, ferns, cacti and succulents, bulbs, ground covers, and some tropical plants all fall under this herbaceous heading. Certain types of plants lend themselves better to achieving particular landscape goals. Botanical definitions can help provide clarity in understanding these types of plant material.
Annuals
Annuals are commonly used in the landscape to provide color and seasonal interest. A true annual, in the botanical sense, completes its life cycle in one growing season. It starts from a seed, blooms, produces seed, and dies. These are often popular plants for gardeners since they tend to be heavy and colorful bloomers, and many maintain their vibrant floral display throughout the growing season. However, we use many plants as “annuals” that would actually be perennial in warmer climates. Petunias and impatiens, for example, continue to bloom and produce seeds for many years if not killed by low temperatures, insects, or disease. We also use many tender plants with colorful foliage as annuals, such as coleus, alternanthera, sweet potato vines, and dusty miller. Some of these would be perennial plants in frost-free zones.
Biennials
Like annuals, the role of biennials is often to provide splashes of color that can be used to add interest to the garden across the seasons. Biennial plants are less common, but some, such as foxglove and hollyhock, are beloved by gardeners. Many naturalized wildflowers are also biennials, including Queen Anne’s lace. The term biennial refers to the plant’s need for two growing seasons to complete its life cycle. The first year is devoted to vegetative growth and the second to flowering and producing seed before dying. Many people think this cycle of growth means the plant needs two years before producing flowers, but in nature that is often not the case.
As an example, the seed from a hollyhock ripen and fall only weeks after the plant has flowered. This seed germinates before autumn frosts and produces a basal rosette of foliage by the time winter has arrived. This basal rosette receives the amount of winter chilling needed to vernalize the plant, which conditions it to send up bloom stalks as soon as weather warms the next spring. Therefore, the fall growth is the vegetative state, and spring brings thee reproductive flush of growth that produces the bloom. This pattern is common in many biennials that accomplish two seasons of growth in only one calendar year. This growth and reproduction cycle explains why many wildflower mixes are recommended for fall planting so that color will be provided the following spring and summer.
Perennials
Perennials may live for many years, even decades, although some are not that durable. The life span of some shorter-lived perennials is genetically determined, while others may be poorly adapted to the region or poorly sited in the garden. Perennials have gained significantly in popularity in recent times for a variety of reasons. Some gardeners choose to spend money on perennial plants that will endure for years, while others prefer the appearance and function of annuals in their gardens.
The terms tender perennial or half-hardy annual are sometimes used to describe groups of plants that will survive mild winters in the area but are killed by colder temperatures. If planted a zone further south, they would probably be rated truly perennial.
Grasses
Annual and perennial ornamental grasses often play aesthetic roles in traditional flower beds and can be used in more functional design applications. Like shrubs, they may be a component of a foundation planting or a screen planting. Planted in a mass, they serve as ground covers. Grass selections available at better nurseries have expanded exponentially in the last few years as their popularity has grown.
Ground Covers
Herbaceous ground covers are usually perennials that keep their foliage throughout the winter, though deciduous perennials may also be used in this role. Ground covers may provide solutions for a design or site challenge. For example, they can be quite useful in an area that would be awkward or too steep to mow, or in places where turfgrass will not succeed. They are often used as a base in shrub beds or under trees, but they may also be an effective part of flower bed design. The ground cover most people think of first is the ubiquitous monkey grass, but there are many plants that can serve this function. Consider using ground covers for broad brush strokes of color rather than outlines at the edges of your beds. They can be used as part of the composition, serving as elements for contrast or complement.
Tropicals
Tropical plants were once relegated to the patio or porch for summer interest or used as houseplants. These are certainly still viable functions, but tropicals are gaining much wider use in summer flowerbeds and mixed containers. They add a lushness and bold effect that many gardeners find exciting and difficult to replicate with other plants. They may be wintered over in the home, greenhouse, enclosed garage, crawlspace, or other protective structure. However, gardeners most often consider them a part of the annual expenditure for color, and they purchase new tropical plants each spring.
Keys to Success with Herbaceous Plants
Choosing Plants Appropriate to the Region
Plants should be selected that are suitable for Tennessee in general and for the gardener’s region specifically. Some may not be tolerant of summer heat, or they may be tender perennials that will not consistently survive winters. In Tennessee, hardiness zones range from 6a in the eastern mountains and portions of the plateau to 6b and 7a across much of middle and West Tennessee. Some areas of southern Tennessee, especially around Memphis and Chattanooga, are zoned 7b or even 8a in urban areas.
Identification of growing zones and understanding of environmental conditions is the first step in narrowing the scope of appropriate plants for use in home gardens across the state. Discovering which plants will be well suited to a specific region is the next step in the process. The University of Tennessee Extension offers a wide range of resources and publications to assist with researching plant recommendations for all growing zones in the region that are available to the public at UTHort.com.
UT Gardens, the official botanical garden of the State of TN, also offers a wealth of resources. UT Gardens has three locations across the state: Knoxville, Crossville, and Jackson. Each garden’s location provides a great point of comparison for the diverse growing conditions found throughout the state. Visiting a nearby UT Garden site can offer valuable insight into plants that thrive in local conditions. The gardens are free of charge and open to the public year-round.
Each garden location has a unique personality and focus. UT Gardens Knoxville, the first to be established, features a mix of themed gardens and areas for educational demonstration, trials, and research. UT Gardens Jackson features unique plant collections, perennial and woody plant trials, and creative displays of seasonal color that are evaluated annually for performance. Annual trial results for Jackson and Knoxville garden locations can be found on the UT Gardens website at utgardens.tennessee.edu. UT Gardens Crossville features demonstration gardens, an interactive children’s learning garden, and research observation plantings. All three garden locations make a strong effort to identify plants with labels and provide additional education through descriptive signage, maps, and interactive online tools. They also host educational field day events, and plant sales throughout the year.
Site Selection
In choosing sites for plants, keep in mind the variations in light categories and the time of day during which plants will receive direct sunlight. Finding the environment to meet the needs of your plants can sometimes be a learning experience. A recently purchased plant may be listed as suitable for part shade, but when it is planted in a site with shade in the morning and sun in the afternoon, it may not perform well because of the intense afternoon sun. Although the sun exposure of the site is technically considered part shade, there are large differences in heat and light accumulation. It is often best to find the plant suited to the desired site rather than try to find the right site for an impulsive plant purchase.
One of the benefits of herbaceous ornamentals is that many have small root systems, making it possible to transplant them if site conditions appear less than ideal. Be knowledgeable about the site factors that can influence survival of plants. Choose plants according to the amount of sun or shade and soil moisture at the site (see photo below).
Coming to understand the growing site and the plant material can sometimes involve trial and error. Maintain optimism, though, because there is likely a plant that will thrive in any given environment. For example, see the sections entitled “Herbaceous Plants for Sunny Sites,” “Herbaceous Ornamentals for Dry Sites,” “Herbaceous Ornamentals for Shade and Part Shade,” and “Herbaceous Ornamentals for Poorly Drained Sites.”
Purchasing Plants
Annuals are often sold in cell packs, which are plastic trays divided into sections containing four, six, or eight plants per pack. Annuals are often called bedding plants, which refers to the common practice of planting large quantities in a bed to produce a mass of color. For “instant color,” it has become more common to also see these plants offered in 4 to 6-inch pots, quarts, and even gallons, already blooming and able to provide a splash of color immediately upon planting.
Perennials are not often found in cell packs. They are usually offered in quart or gallon containers, although you may find them as seeds, tubers, bulbs, roots, or corms, and sometimes as bare-root plants. Seed packets provide important information for seeding and young plant care. Pay special attention to the temperature required for germination because improper temperature is a key reason many gardeners fail in home seedling production. Proper moisture and light levels are also very important in enabling germination and promoting the health of young plants. (see Chapter 11 for information on transplant production.) Many commercial products, such as trays, domes, and heat mats, can help promote seed germination.
Herbaceous ornamental plants sold as tubers, roots, corms, or bulbs may benefit from immediate planting, as they can dry out or begin to decay if left open to the air. However, other types can be stored for later planting. Bare-root plants should be planted immediately.
Be aware of optimum transplanting times for the various types of plants. For example, spring flowering bulbs should be planted in fall so that they can receive the winter chilling time they require to initiate flowering. Tender bulbs and rhizomes such as canna, caladiums, or dahlia can be stored in a dark, dry, frost-free area to be planted once the danger of spring frost has passed and the soil has warmed. Lily bulbs cannot be allowed to dry out, and, if stored, need to be kept uniformly moist but not wet.
Container plants are most common, and the best time of year to plant them is generally in the spring or fall. Fall planting of very hardy perennials has the benefit of exposing the plants to cooler temperatures and more abundant rainfall, which helps them to become established. However, if the plant is one that might not survive a Tennessee winter unless well established, it would be best to plant in spring.
Here are some additional tips for buying plants:
- Select plants that are uniform and balanced to the size of the container. Weak, elongated, or flopping stems are a sign that the plant has been grown too tightly packed with other plants or has been in the container too long.
- Resist the temptation to choose the plants with the most flowers. One that has yet to bloom or has many buds that have not yet opened will provide more weeks of color. If it is a plant that continues flowering throughout the summer, it can be deadheaded while it adjusts to its new site so that the energy can go to root and foliage growth rather than to the blooms.
- Select plants with healthy foliage of good color. Look for insect damage or areas of discolored, dark, or rust-colored spots, as these may be signs of disease.
- Inspect the plant for insects. They may be hiding on the underside of the leaves as well as on stems and leaf petioles. Aphids, spider mites, mealy bugs, white flies, and scale are common insects found on plants. To help detect pests, tap or shake the plant lightly and note whether any of the pests fall off.
- Inspect the root system to make sure roots are healthy by gently removing the plant from the container. Press on all sides of the container to loosen the roots so the plant slides out easily. Then look to see if the roots fill the container without being root-bound. Root-bound plants have an overabundance of roots circling the pot, which will hinder establishment when transplanted. Brown or discolored roots may be diseased or rotted. Healthy roots are whitish.
Bed Preparation and Weed Control
In a perfect world, soil would be weed free and moist but well-drained. It would contain adequate organic matter and biological activity. It would have an ideal pH and contain the nutrient elements needed for healthy plant growth. One of the challenges and blessings in gardening is the fact that no soil is perfect for every plant. On the other hand, there are likely to be plants well adapted to a variety of soils. Across the state of Tennessee, there are a wide range of soil conditions, including loamy, clayey, rocky, sandy, or any combination of these. Gardeners have the option of selecting plants that can survive and thrive in existing soil conditions or try to create soil suitable for other plants they prefer. Soil amendment and management can improve conditions over time (as discussed in Chapter 6), but many aspects of soil improvement can be costly and time consuming.
Soil pH and Nutrition
Broad optimum pH ranges for herbaceous crops are from 5.5 to 7.5, but it is reasonable to try to keep the pH level between 6.3 and 6.8. Although individual flowers can differ in their soil pH preference, this pH range will be acceptable for adequate nutrient uptake by a large variety of species. Likewise, nutrition needs can vary among species and between annual and perennial crops. Refer to Chapters 5 and 6 for information on soil sampling and testing as well as on the use of soil test reports.
Soil Drainage and Raised Beds
A well-drained soil does not allow water to stay in the root zone of plants for long periods of time. Percolation tests (described in Chapter 7), along with estimates of available water-holding capacity (see Chapter 5) can be useful in assessing the drainage qualities of the soil at a particular site. Herbaceous perennial plant losses often blamed on cold temperatures are frequently the result of poor drainage. While drainage can certainly create issues during the growing season, it also exacerbates the effect of cold temperatures when plant roots or crowns are sitting in poorly drained soil during the winter (see page 9-14). The importance of soil drainage is one reason that raised beds are successful and common for ornamental beds as well as for edible crops.
Organic Amendments
Organic matter is crucial to soil quality, productivity, and sustainability, as described in Chapters 4, 5, and 6. Organic matter in the soil provides nutrients, moisture retention, and good air and water movement to promote root health and plant productivity. Organic matter content can be increased by adding compost or manures and by the use of mulches. Horticulturists often recommend the addition of organic material before planting to enhance the establishment of young plants. However, many plants can thrive or even prefer soils low in organic matter, such as some herbs and a number of our “roadside” natives.
A drawback of heavily amending the soil in planting areas is that rapid root growth occurs in the enriched soil, with reduced growth in the nearby unamended area. Plants that have reduced root presence in the surrounding native soil could be limited in water and nutrient availability over the long term and may require more watering and maintenance.
Herbaceous ornamentals tend to have a smaller rooting area than woody plants, so amendment practices may be better suited to beds that contain a majority of herbaceous plants. If a quick burst of seasonal color is the design objective, soil amending can help achieve that effect. See Chapter 8 for a discussion of bed amendment practices for ornamental planting beds. Decisions about the level of soil amendment should be made with a thorough knowledge of the current soil conditions, as well as the needs and growth habits of the plants to be placed in the beds. Also, be aware of subsequent maintenance requirements, such as irrigation, to maintain healthy and productive plants.
When soil is amended, high-quality organic materials such as composts and sometimes aged manures that will slowly release nitrogen can be used. Fresh manure can burn plants because of its high nitrogen levels. Be aware that not all plants like manure, as it can alter the pH.
Weed Management Before Planting
Creating a weed-free ornamental planting area can be a challenging task. Eliminate any existing weeds before planting. In a small area, hand pulling and digging of weeds may be the best approach. Be sure to remove all stolons (runners) from weeds such as Bermudagrass before tilling, as tilling will break stolons into smaller pieces that can quickly reestablish. If grass is the only weed problem, a selective herbicide that kills only grass can be used without risking damage to nearby plants. If there is a variety of weeds, a nonselective herbicide is in order. Be sure to observe the proper waiting time for the weeds to absorb the herbicide before planting the desirable plants. Keep in mind that multiple applications may be required for some planting areas and vegetation types.
Please read and follow all herbicide label directions for proper handling and timing (as described in Chapter 15). If several months are available before planting, a cover crop can be grown and then later tilled in to add organic matter and reduce weed pressure. Also, lasagna gardening, or sheet mulching—a type of composting on top of existing grass and weeds can allow immediate planting.
Establishment
Spring and fall are generally good planting times because the milder temperatures create a less stressful environment for plants than in summer. Under cooler temperatures, plant roots dry out slower and less water is lost through leaves. Even when the moisture level is ideal, hot temperatures can stress plants. For good plant establishment, the soil should be kept uniformly moist but not wet. Planting in wet soil can lead to compaction from human traffic in the beds and deprive young roots from needed air exchange, leading to disease and root death. Good watering practices are the result of careful attention. Strive for not too wet, not too dry, but just right.
Plants should be spaced according to their expected size at maturity. When planting from containers, try to match the soil level in the container with that of the native soil in the planting site. Planting too deep deprives roots of air exchange and can encourage crown rot. Placing the plant too high will dry out the roots.
Plants grown in containers often tend to continue to grow in the shape of the container after planting. Roots need to grow into nearby soil in order to take up water and nutrients and to anchor the plant into the soil. To encourage this growth, cut slits in the side of the root ball, or gently pull the roots apart with the fingers (see page 9-12). After planting, thoroughly water the area to remove any air pockets and to settle soil. Be careful not to cover the crown of the plant with any subsequent mulching materials, but do mulch over the top of the roots.
Aftercare
Watering and Irrigation Management
lants need adequate water to remain healthy and vigorous throughout the growing season. There can be no “recipe” (standardized timing) approach to watering schedules, as many different factors determine water needs. Location, weather conditions, soil type and temperature, day length, stage of growth, and moisture preferences of different species all play roles, so pay attention to specifics. For example, slopes and sunny sites need more water than plants in low, shady areas.
Think of the yard as a series of microclimates. The house, trees, shrubs, and structures all affect how much the sun, wind, and temperature affect the herbaceous ornamentals. Also consider root competition because herbaceous ornamentals near trees can need more water than those in an open bed. Remember that the sun changes position in the sky throughout the year, so different seasons may require more or less watering as shadows change in relation to the planting bed, and as day length shortens. Plants in containers need water more often than plants in the ground.
Drooping or wilting leaves do not automatically mean that the plant needs more water. It may be very hot outside and the leaves are losing moisture faster than the roots can pull it from the soil. Watering a plant that already has sufficient soil moisture can lead to root rot and other diseases. Water if the soil feels dry, but do not wait until it gets bone dry, as it can be difficult to rewet and soften so that it can absorb moisture. Feel under the mulch and immediate soil surface to determine moisture needs. After plants are established, water for longer periods at less frequent intervals. Deeper watering encourages roots to grow deeper into the soil to find moisture. Frequent and shallow watering is not recommended because it encourages roots to develop near the surface of the soil, which makes the plants vulnerable to drought conditions.
The ideal time of the day to water is when plants need it. Morning is often ideal as the cooler soil leads to less evaporation and better absorption.
Fertilization
Fertilizers can boost growth and flowering, but too much nitrogen can result in more vegetative growth than reproductive growth (blooms) in many annuals and perennials. Choose a “bloom starter” formulation that has more phosphorus and potassium, such as a 5-12-12. Some herbs and plants suited for rock gardens prefer relatively infertile soils and may actually decline if fertilized. Carnivorous plants such as pitcher plants are examples of others that should not have supplemental fertilizers, so do not assume that adding fertilizer is always good practice. Even for those that respond well to fertilizer applications, it is best to be sparing, as too much fertilizer can be detrimental or even deadly.
A variety of fertilizer formulations are available for herbaceous ornamentals. Slow-release fertilizers extend nutrients to the plant over a period of time. Water-soluble fertilizers release nutrients immediately to the plant, but the nutrients leach out quickly, so a combination of slow-release and water-soluble fertilizers can be an asset.
Apply slow release fertilizer according to label directions in the early spring. This one application may be all that the plants require throughout the growing season. Water-soluble fertilizers can be used any time, especially when plants exhibit signs of nutrient deficiency. If annuals, tropicals, and perennials start to have yellow leaves and not look vigorous, fertilizer may be needed. However, be sure to inspect for other causes of poor performance, including soil moisture or disease of the roots or crown.
Fertilizer should not be applied to perennials in the late summer and fall because it stimulates plant growth. In the fall, herbaceous ornamentals need to go dormant in preparation for winter, and late-season growth can reduce winter hardiness.
Pest Management
The principles of integrated pest management, described in Chapter 13, are the best starting point in dealing with plant pests. Choose pest resistant plants and site them optimally, using recommended cultural practices that reduce stress, with special attention to proper watering.
Scout plants regularly for problems, but use discretion before deciding on treatment. A certain amount of cosmetic damage may be acceptable. This is especially true when the impact on pollinators and other wildlife is taken into consideration. In fact, chewed leaves are a symbol of a successful butterfly garden if the chewing was done by their caterpillars.
If damage or discolored leaves are found, use the diagnostic procedures detailed in Chapter 13 to determine if the cause was abiotic or biotic. Biotic problems can then be narrowed down and a decision made as to whether control measures are necessary, and, if so, what approach works best with least detrimental impact.
Good sanitation is another way to reduce disease pressures. Remove diseased plants and their debris to eliminate sources of inoculum. Promote air flow and access to bright light by thinning or pruning to make conditions less favorable to disease. Attract a diversity of wildlife to encourage good predator-prey relationships in the garden, which reduces insect pests. Be aware that spraying for a pest can kill the predators that could have kept the pests to a reasonable number, and these predators will not rebound as fast, resulting in a ballooning pest population.
Pruning and Plant Management
Deadheading and Cutting Back
Removing spent blooms, a process known as deadheading, prevents the plant from producing seeds and encourages new flowers to develop. Deadheading makes the garden look neat and clean, but if you want seeds in order to propagate more plants, leave the blooms to mature. Some flowering plants have greatly improved performance when regularly deadheaded while others do not need it or show no benefit. Also be aware that some of the spent flowers and seed heads can actually be attractive and provide textural or structural interest to a winter garden. (see photo on page 9-18.) Others may provide seeds for foraging birds.
The foliage of most perennials dies in the winter. If the dead foliage is not attractive as part of the winter garden, there may be some benefit to cutting it back in the fall or winter to reduce the overwintering of insects and the presence of diseases in the spring. However, for some species that may be more sensitive to winter weather challenges, the standing foliage can offer a bit of protection that may make a difference in surviving cold temperatures. Several fall-blooming perennials, such as asters and chrysanthemums, will get bushier if cut back during the summer. Remember to cut these perennials back before the beginning of July so they have time to develop flowers to bloom for the fall. Some of the tall perennials that have a tendency to flop over can also be cut back in early summer, which can result in a bushier, stronger plant, though it may delay blooming a bit.
Dividing
Dividing is a method of separating a plant into two or more pieces containing root and shoots. If flowering is waning and the plant seems less vigorous or has gotten too large for the area, it needs to be divided. Many gardeners divide plants in the spring when temperatures are not too hot and other types of garden maintenance are occurring. Dividing can also be done in the fall, but care should be taken to provide adequate moisture, as fall is often the driest time of the year in Tennessee. Use a garden spade to dig the plants to be divided. Once plants have been dug, use a spade, knife, dull pruning saw, garden fork, or one’s hands to separate the plant into pieces. Make sure to get one or more stems, or eyes, per division to ensure survival.
Weed Control
If your plants like growing in a site, then it is quite likely that weeds will also like growing there. Even seeds from last year’s annuals germinating in the wrong area can be considered weeds.
A well-mulched garden prevents many weeds from germinating and makes it easier for those that do invade to be removed. Weeding on a regular basis helps keep weeds under control. Weeds can be pulled by hand or removed with the aid of a hoe or other garden implement, but make sure to get the entire root system. There are preemergent herbicides available that control many common germinating weeds but be aware that pre-emerge herbicides will also prevent reseeding from desirable annuals or biennials. Read and follow label instructions for application rates and species around which the herbicide can be used. See Chapter 15 for additional information.
Mulching
A thin layer of mulch, usually 1 to 2 inches, can be sufficient to create an insulating blanket over the ground to protect roots from temperature and moisture fluctuations. This covering also aids in controlling weeds, and it unifies and defines the garden design.
Many types of mulch are available. The type chosen should be based on specific needs and demands of the site and gardener. Shredded hardwood, pine bark, shredded leaves, and pine needles are the most popular forms. As they decompose they provide valuable organic matter to the soil. Since these organic mulches break down, they must be reapplied annually or semiannually. Inorganic mulches such as rock are more permanent and do not need to be replaced as often, but be aware of the danger that rocks may be slung by mowers or string trimmers. Also, certain types of rock can affect the soil pH.
Landscape fabric can be a problem over time as it is usually placed over soil, then covered with mulch. If weeds germinate in this mulch they become firmly anchored through the landscape fabric into the soil and are very difficult to remove. Also, the fabric is very unattractive if exposed, and it can cause problems if it inadvertently gets wound around the blades of a mower or tiller. In certain situations, landscape fabric may be used under a layer of gravel or stone to prevent these materials from working into the soil, but be quick to remove any germinating weeds. Plastic is not recommended as a mulch.
If installing plants in 4-inch pot sizes or smaller, placing mulch down first to cover the bed will be better for the plants and less work. It is easier to move a small amount of mulch away from the planting area and place the plant even with the soil surface than to apply the mulch once the plants are in place. The small amount of displaced mulch can easily be placed back around the plant.
Using Herbaceous Plants in the Landscape
Designing with Herbaceous Ornamentals
Colorful flowering plants are irresistible to the gardener, but good design principles employ the use of line, form, and texture as well as color to organize a pleasing composition (see adjacent photo). An old-fashioned “flower bed” can be less interesting than a savvy composition that lets other plants—such as shrubs, grasses, and tropicals—play design roles. Let evergreen shrubs and perennials form anchoring year-round backdrops. Choose plants that create a dynamic work of art that changes from season to season. (see Chapter 7).
Color
A house interior is often organized thoughtfully around color, and this same thinking can prevent a garden from becoming too raucous with competing hues. Do not be afraid of using bold contrasts and complementary colors, but it may be more appealing to play with color themes, such as contrasts of blue and yellow, or a garden filled with complementary shades of pink. Sometimes a carefully planned monochromatic planting can provide as much interest as a multicolored grouping.
One advantage to designing with herbaceous ornamentals is that they are easy to move if one wants to change a color or a texture. Many gardeners change their herbaceous beds on a regular basis as new and interesting cultivars and varieties of plants become available, and many do so just for fun with annuals each season. Using primary colors of blue, red, and yellow can add vivid hues to the garden. Much has been made of the “rules” suggested by the color wheel, but “suggested” is the operative word. Breaking rules can lead to breathtaking results. The most important criterion is what pleases the gardener’s eye.
Texture
If a planting looks a bit humdrum, texture can provide lots of opportunity for delight. The texture of plant leaves and blooms can be coarse, medium, or fine, and those textures can be used in contrasting ways to intrigue the eye. Imagine wispy grasses shimmering behind bold leaves of canna, or arching ferns among caladiums. Adding woody ornamentals for a textural element can provide more options to the tableau.
Just as with woody plants, the herbaceous plant’s form, or growth habit, should be considered for its impact. Consider how many garden plants are mound shaped, and the dramatic effect created by adding plants with a dramatic spikey or vertical form. Certainly, woody plants can serve this role, but so can many herbaceous plants. Think of hollyhock, liatris, and red hot poker.
While some of the taller options might be best relegated to the back of the border, do not let that placement be binding. A tall selection placed farther forward can have an arresting presence, plus it might provide a spot of midday shade for another plant that needs shielding from the hottest hours. Tall plants do not always obscure those behind; for example, the red star hibiscus can tower over the visitor’s head, yet the base of the plant is relatively narrow and the foliage is airy and widely spaced. This creates a breezy “see-through” plant that does not hide its neighbors.
Use lines to create a sense of order or to pull the eye smoothly through a planting. These lines can be the actual shapes of the beds, the paths that move through or alongside, or a sweep of one particular plant or color. However, do not fall into a predictable monotony of an edging of low plants, backed by a medium-sized species, backed by a taller form. This placement can result in a tiresome overall effect of “stripes” in the garden.
Perennials
Bulbs
In gardening terms, the word bulb can be used in a general sense to describe the entire group of geophytes, plants that use underground organs for storage. Technically, they can be broken up into corms (crocus, for example), rhizomes (in the case of iris and daylily) or tubers (such as dahlia and peony). True bulbs have layers like onions, and they include daffodils and tulips. For the sake of brevity, this chapter addresses them all as bulbs.
Bulbs can be selected that provide excitement for any season of the year, but spring and summer bulbs are most popular with gardeners.
Spring
Among the dizzying array of spring flowering bulbs, perhaps none is better known than narcissus (daffodils). There are seemingly countless varieties. Early-, mid-, and late-season forms can be used to extend the bloom season. They may be chosen for size, fragrance, and a range of white, yellow, and peachy hues. So many different types are offered that it behooves the gardener to research them further for regional favorites. A great source of information is the American Daffodil Society, and representatives can be found in each region of Tennessee.
Tulips can provide some of the most vivid color of the spring bulbs, but be aware that most tulips used for big impact are not reliable perennial performers. Our climate is simply not suited well enough for them to store the energy needed for repeat blooming. A little research reveals that there are a handful of varieties that are said to repeat for some gardeners. They may be worth trying, especially some of the “species tulips” that have their own appeal, if not the impact.
Other spring bulbs of note include crocus, iris, hyacinth, snowdrop, and squill. Some alliums are spring bloomers.
Some general culture tips can help the gardener achieve success with spring flowering bulbs. A period of winter chilling, also called vernalization, is necessary to stimulate growth and flower production. This chilling can occur outdoors in the soil on the desired site, or the bulbs can be chilled in a refrigerator for at least 8 to 10 weeks before planting. Sometimes bulbs are offered as “prechilled” for potting up indoors during the winter, a practice called forcing, very common with a daffodil often called “paperwhite”.
When choosing an outdoor site, remember that the foliage remaining after the flowering display must be allowed to remain for at least several weeks so the plant can store enough energy for next year’s bloom. Sunlight is necessary for this process, and locations under deciduous trees are good places for bulbs, as they can receive enough light before the trees develop their leafy canopies. Marking the bulbs’ location is wise so that they will not be disturbed during dormancy.
Plant in well-drained soil three times the depth of the bulb, counting the bulb itself as one-third of that depth. Bulbs planted too deep may not surface or may not bloom. In fact, dividing bulbs and planting shallower can be of benefit with clumps of older plantings that have no or fewer blooms.
The clumps of foliage from spent bulbs should be left in place until they begin to yellow and wither, signifying that enough energy has been stored. Factor the time for this process into the design, perhaps planting other perennials with handsome foliage and later blooms among the bulbs so that they are obscured during this unsightly period. Remember that the bright spring flowers are present only briefly, so it may not be wise to let them take a front and center role. Braiding the foliage to get it out of the way is not advised.
Summer
Again, plants lumped together as “summer bulbs” are often rhizomes, tubers, or corms. Some are used for flashy tropical foliage such as caladiums, used purely as annuals. Elephant ears and cannas also offer lush, bold foliage to the summer garden. Some of these are perennial, while many are not. Investigate the particulars on each cultivar and site carefully in marginal areas of cold hardiness.
Cannas are prized for their large showy foliage as well as flowers, and they range through hot colors of yellows, pinks, oranges, and reds. They can grow knee high or may tower overhead, depending on the cultivar. Dark foliage is not uncommon, with some nearly black and others offering bright striped leaf variegation of golds and reds. They can be grown in average soil, but they love a wet site and can be great solutions for areas of poor drainage.
Crocosmia adds fire to the late summer garden, flowering in bright warm hues of red, orange, and yellow. The foliage is linear and handsome. These are very hardy plants for sunny, well-drained sites, and they are quite drought tolerant.
It would not serve the purpose of this manual to delve deeply into the world of lilies. There are many species, and so much hybridization has taken place that no attempt can be made here to account for them all. Many gardeners concentrate on a few groups—the Asiatic lilies, the Orientals, and the trumpet lilies. “Orientpets” have combined some of the best characteristics of the latter two. A few species lilies are favored as well, such as the Formosa lily and the martagon. The old “tiger lily” of heirloom gardens is tough as nails, though lily collectors disdain it because it may carry a virus that does not affect its appearance but can spread to damage other lilies. The North American Lily Society offers much more information, even listing the most popular and “hall of fame” species.
No discussion of summer bulbs would be complete without a mention of crinums, sometimes called crinum lilies. Many of these can outlive the gardeners that plant them, eventually forming massive bucket-sized bulbs. Interest in them has revived in the trade, and many different forms can be found in specialty catalogs.
Gardeners who love cut flowers may enjoy Gladiolus. Many of the types found in the florist trade are not reliably hardy in many parts of Tennessee, but some cultivars show up year after year. Sources for “hardy glads” are easily found online. A separate species, called Byzantine glads, have demonstrated durability by decades of performance around old homes in Tennessee.
Perennial Plants
While many plants fit the botanical description of perennial, the terms perennial garden or perennial plants have come to represent a certain style of gardening, used to create colorful vignettes of herbaceous plants. Often they are used to create an ambience known as a cottage garden, and newer evolutions have more of a prairie feel, using more grasses and less reliance on bright-hued flowers.
These perennial plants are grown for flowers, foliage, or both. Some gardeners have elected to specialize in them to save money “because they come back every year.” Regrettably, that is not always the case. It may be that a certain plant is a reliable perennial in another climate but not in Tennessee’s challenges of heat and humidity. Other perennials are known as “short-lived,” and no matter how ideal the climate and soil are, they simply have a briefer life span. Other times it might be that the plant simply was not happy in a particular site and would prosper if planted in another spot.
UT Gardens at Knoxville, Crossville, and Jackson maintain extensive perennial beds where plants can be perused throughout the seasons for beauty and performance. You can find annual reports at their websites of the “best performing,” along with several years’ archives of the “Plant of the Month.” The Perennial Plant Association is also an excellent resource for perennial information. Remember to design for seasonal excitement. Although some perennials have brief bloom seasons, that is not necessarily a negative trait. A garden that heralds the turning of the year with distinctly seasonal flowers is never boring. It is also true that many perennials add handsome foliage, and flowers are not their best contribution. They are helpful to conceal tattered foliage of those plants that are less than attractive once past their seasonal hurrah.
While it is always fun to try new or improved perennials, one of their assets is that they can often be divided to create more plants for the garden or to share with other gardeners. Each species may have particular needs for timing and method of division, so research them beforehand. Master Gardener plant sales and swaps are a great way to get starts on divided plants that have been so successful with fellow gardeners that they have plenty to share. But also be aware that it may mean this particular plant is so vigorous and spreading that it may become an aggressive nuisance over time.
Perennial plants can be planted year-round if they are considered to be very hardy to your region, but if they are marginally hardy, it is best to plant in spring so they may be well established before the onset of winter. Often, perennials can be found on sale in the fall, as nurseries do not want to bother with overwintering them. The procedures for loosening roots and developing adequate watering regimes are similar to those for woody plants, as described in Chapter 8.
Ferns
Annual ferns often fall into the “houseplant” genre, but many are used in seasonal summer displays. In urns or hanging baskets, large Boston ferns are a tradition for many homes during frost-free months. Kimberly fern and Macho fern are more tolerant of sun and a bit less demanding on watering. Golden forms of Boston fern can be fabulous in container combinations for summer.
Perennial ferns can be fabulous players in shade gardens (see page 9-23). Some may be evergreen—or mostly evergreen—depending on the severity of the winter. They vary greatly in size. They can reach a gardener’s shoulder or barely cover an ankle. Use them as textural counterpoints to hostas and hellebores. Some are clumpers that grow more impressive as years pass, while other spread by rhizomes and may be used as ground covers—cautiously!
Most ferns like shade and good compost soils, as indicated by the woodland floor habitat where many originated, and while they often frequent wet areas, most do not require it and flourish in drier sites. A few, such as the bracken fern and the hairy lips ferns, are surprisingly tolerant of dry rocky sites and bright sun. There is an American Fern Society for gardeners that have a particular affinity for this group of plants.
Grasses
For ages, grasses have benefited humans and the development of stable, fertile soil, and they have supported animal life. As one of the first plants to grow in disturbed areas, grasses help stabilize soils and reduce the damage caused by humans and natural disasters. The diversity in their appearance and adaptability is unequaled by any other plant, and it is no surprise that grasses are found on all continents and Antarctica. Their low growth point allows them to continually sustain damage to the top of the plant by grazing, mowing, and fires without serious damage. The development of ornamental grasses has enhanced the beauty of the garden because of their range of colors and sizes, which are varied enough to meet any landscape need. Most ornamental grasses are adaptive and do well with native soils and environments.
The beauty of ornamental grasses allow them to stand out as the focal point of a plant grouping as well as being part of the harmonious landscape. Grasses are easily moved with the wind and can be a striking addition, even simulating water in a landscape design. Ornamental grasses have texture and form vastly different from other plants, making them a good companion in any garden. Grasses can be used in containers, perennial borders, foundation plantings, and as specimen plants.
A number of exciting annual grasses coming to market have augmented the use of the well-known ruby fountain grass, often used for texture and movement in container plant combinations. Look for some with variegated foliage, unusual textures, and a variety of growth habits, from compact to full-bodied.
Perennial grasses can be very long lived, so good selection is imperative, as they can be deeply rooted and difficult to move or eradicate if no longer appreciated. Qualities that might make a grass undesirable over time could be untidy growth habit, with a tendency to “lodge” —that is, leaning over on garden neighbors. Others have a tendency to aggressively reseed, as exhibited by the miscanthus. Careful attention to cultivar selection can avoid these issues.
Be aware that many of the plants promoted as “grasses” are not true grasses in the botanical sense. Sedges, rushes, cattails, and papyrus are all examples of grass-like plants that are offered for use in ornamental plantings.
Ground Covers
Often touted as problem solvers for areas that are difficult to mow or where turfgrass may not succeed, plants described as ground covers can also be used simply for exciting design components, perhaps as an understory for textural counterpoint, or a sweep of line to pull the eye through the landscape. Indeed a single specimen of a plant normally regulated to ground cover status might be fabulous in a container.
Ground covers that are chosen for spreading habits and evergreen foliage are most useful. Spreading might be the preferable growth habit, but one should consider how the plant spreads. An aggressive rhizomatous plant, or one that rampantly forms vines, can quickly become a liability, overwhelming desired plants, climbing trees, and getting beyond the boundaries desired. Clump-forming types that stay put might be slower to achieve the desired effect, and it may cost more to purchase the number needed for the purpose, but they might be worth the extra investment over the long term.
Be sure to evaluate the site carefully before selecting the best ground cover for cultural conditions. Consider if a mass planting of the same species is a risky investment before plant purchase. A mixed planting can be a way to hedge one’s bets and can also be more visually pleasing. Some ground covers offer seasonal blooms or color changes through the year.
Annuals
Bulbs
Caladiums are the most common annual bulb used for summer color. Not only do they not overwinter, they cannot tolerate even cool soil and therefore must be planted after soils have warmed in late spring. If they are to be kept over for another year, they must be dug and stored before soils cool significantly in fall. Tuberose and dahlia are some of the bulbs that are not reliably perennial and are popular enough to warrant annual replanting each summer.
Plants
Annual plants are probably the main attraction each spring at garden centers, and as those aisles fill, the avid gardener’s wallet empties. Colorful blooms and foliage are the bait, and breeders know it. Each year there may be a new and tempting shade of a favorite flower, or an entirely different species to try.
An important concept for the shopper to grasp is that of a plant series. Breeding may produce a wonderful plant with a particular growth habit and durable performance. Gardeners love it, but perhaps its color is not the one desired in this year’s palette, or they have grown tired of the color. As attempts to produce a similar plant in a new shade succeed, it becomes one in a series. A good example is the Wave petunia, first available only in the shocking magenta known as ‘Purple Wave’. Now there are many colors available in the ‘Wave’ series.
Since the availability of annuals changes so fast over the years, this is an especially important area to pay attention to when studying UT Garden trial garden results. Each year, reports are compiled for industry use and are also made available to the gardener on the UT Gardens website. However, visiting the gardens is likely to be the best experience for developing a wish list. Go at different times through the summer to see how plants continue to perform (or not) as the seasons progress.
Herbs
Herbs are plants used for culinary or medicinal purposes, and plants with a component of fragrance, perhaps used in crafts. Culinary use is likely to be the stimulus behind the boom that herb gardening has enjoyed in the last several years. The foodie movement has fostered the desire to have the singular flavors and color that fresh herbs can give to food.
Many herbs are beautiful plants in their own right and can be used as ornamentals for that reason alone, so gardeners often mingle them freely among other plants without installing a more traditional herb garden. Basil, for example, is an easily grown annual that is a favorite in summer tomato dishes, and the purple-foliaged forms might take the role that coleus otherwise would in accompanying flowering annuals. Perennial herbs can take more utilitarian roles, along with their other attributes. Hardy forms of rosemary, such as ‘Arp’, can be used for evergreen shrubbery on a sunny, well-drained site. Oregano can be used a tough durable ground cover on a dry, sunny slope.
Herbs get their scent and flavor from the oils in their tissues, so most are best suited to sunny sites, with minimal water and fertilizer. Lush growth means more dilute flavor, so plants kept on a “lean” diet will have more taste and scent. If shade is available, some success can be had with parsley, cilantro, and bergamot, among others. Mints and sweet cicely (best in cool parts of Tennessee) are also candidates, but they can be very aggressive, so consider the potential for problems.
Herbal medicine is to be respected. Not only have many herbs been proven to have pharmaceutical qualities, but many of today’s modern medicines were derived from plant sources, such as aspirin from willow bark or digitalis from foxglove. Using herbs for treating health issues is tricky, however, as it is difficult to ascertain exactly how much active ingredient can be obtained from a given plant. While a little might be beneficial, too much may be toxic. Therefore, UT Extension does not offer recommendations on herbal usage.
The Herb Society of America has a very active chapter in Nashville, and Memphis has an herb society of its own. These meetings are noted for their interesting and delicious foods at break time.
Tropicals
Tropical plants may be perennial and live for many years in their regions of origin, but the colder climate of Tennessee renders them annual. Most will need protection once temperatures fall below 50°F. Some gardeners are willing to overwinter them in the home or garage, or they may find a friend with a spot open in a greenhouse. Others elect to toss them on the compost and purchase anew next summer. The latter option may be more tempting when it is seen that most tropical plants languish during the winter months and may take several weeks to recover once placed back into the summer designs. Exceptions may be some of the begonias, which can make nice house plants if provided bright filtered light and adequate humidity. Others, such as Bolivian begonia or tuberous begonias, have a required winter dormancy.
Many tropical plants are noted for bright, large, and interesting foliage, adding lush texture and color to the landscape during warm seasons of the year. They should not be placed outside until after the last chance of frost in spring and can be planted in containers or directly into planting beds. If containers are buried in the ground, it can reduce watering needs, and they may be dug for winter storage. Most prefer organic, moist, but well-drained soil, though many such as canna or elephant ear are even lusher in wet sites.
Containers
Gardening in containers can allow anyone to garden whether they have a yard or live in an apartment. Any type of vessel can be used as a container as long as it can hold soil, water, and plants and allows for drainage at the bottom. Generally, anything that can be planted in the ground can be planted in a container. The environment, growing media, and moisture level can all be controlled by the gardener. It is likely the ability to control these factors that makes container gardening so popular and successful, with fewer issues experienced than when plants are grown in the ground and exposed to less-than-ideal situations.
Containers can be placed anywhere there is sufficient light for growing plants. The environment chosen can be sunny, part shade, or shady and can be tailored to the needs of the selected plants, or the plants can even be moved to a better site if needed.
Proper watering is crucial. The size of the containers, the type and age of plants, and the growing media used in containers are major determinants in how often they need to be watered. A good potting medium has a thoughtful balance of components that help retain water, such as peat moss or compost, mixed with coarse particles that help keep the mix porous, allowing air exchange to the roots. This coarse component might be finely milled pine bark, perlite, or both.
Sand in the soil mixture also contributes to air exchange, promotes drainage, and can add weight to the mix. Weight can be desirable to prevent top-heavy plantings from toppling in the wind. Rocks and bricks can be used at the bottom of a container for weight if needed. Some gardeners like to add some garden soil to the container for the weight component and for the natural nutrients it can supply.
Watering regimes are also influenced by weather, day length, and stage of plant growth. Plants should be watered when the growing media begins to feel dry. Wilting leaves may not always mean the container needs water, as this can happen in warm breezy weather even when water is plentiful around the roots, as the plant cannot replace the moisture as fast as it is lost. It will lose the wilt as the day cools in the evening.
Plant level with the top of the soil in the container. It’s a good idea to keep the growing media in the container at least 1 inch from the top to retain water without spilling over the top of the container. A slow-release fertilizer can be added after planting, and a second application may be needed later in the season as frequent watering leaches out nutrients.
To create an eye-catching container, remember the rhyming aspects of thrillers, spillers, and fillers.
- Thrillers are the focal point plant of the container. They are usually tall and sculptural, and they catch your eye. Woody ornamentals, grasses, or bold tropicals are sometimes used as the “thriller” parts of a container.
- Spillers are plants that grow over and down the sides of the container. They may be cascading flowering plants, mannerly vining plants, or even ground covers with a spreading habit.
- Fillers are plants that fill in the container. It is fun to use those with contrasting textures and colors from the thrillers and spillers. This is the fun part, where the gardener can play with these elements to create a dazzling combination.
Vegetables and herbs can also be used in these contexts. Spring, summer, and fall-blooming bulbs can be added to a container. Woody plants may provide the needed foliage or form and then be transplanted to the garden later. Be sure they like the same type of watering regime and light environment, although remember that particular plants prefer the “shady side” of a sunny pot. This attention to detail helps create a successful, eye-catching container.
Stewardship Practices
Soil and Water Management
One of the key aspects of stewarding any landscape is the intentional management of soil quality. The ability of soil to infiltrate, move, and hold water is vitally important to plant survival and productivity as well as water quality. Many management steps can be taken to improve soil-water relations.
Site preparation involves addressing compaction and drainage issues through the incorporation of organic matter and other techniques. (see Chapter 4). After planting, maintaining soil cover with mulches is one of the most important soil and water stewardship tactics. Organic mulches are the most useful because in addition to reducing erosion and improving water infiltration, they also slowly break down to add organic matter to the soil. Over time, mulches encourage the multiplication of soil organisms by providing energy sources as well as more even temperature and moisture in their habitat. Increased organic matter further enhances water-holding capacity, and it holds and supplies nutrients for plants, which can be thought of as a beneficial ‘snowball’ effect. Over time, these practices can reduce the need for both irrigation and fertilization in planting beds while also preventing runoff to nearby waterways and storm drains.
One final note about water, soil, and mulching: some gardeners lay a weed barrier in the form of plastic or cloth under the mulch in their flower beds to prevent weed growth. This practice is discouraged for several reasons. First, plastic especially can reduce or prevent water from soaking into flower beds, which can lead to plant stress or death and increased runoff. Second, plants are further stressed by a reduction of oxygen in the root zone. Third, once the mulch decomposes, weeds readily grow in it on top of the weed barrier, defeating its purpose. Finally, weed barriers can reduce the ability of soil organisms, like earthworms, to create tunnels and move organic matter down in the soil profile and improve soil quality. They also complicate planting and dividing as well as plant movement in landscape beds.
Plant Selection and Placement
Stewardship of wildlife, pollinators, and beneficial insects in home gardens can be achieved through thoughtful planning and strategic management of herbaceous plants in the home garden. Including a diverse combination of plant species that provide a wide range of benefits throughout the season is critical for maximum impact. Herbaceous plants provide far more than just nectar and pollen; they can also supply seeds, foliage, plant debris, and leaf litter. These features serve as potential sources of food, nesting materials, overwintering sites, and protection from the elements.
Butterfly species depend on host-plant relationships for survival, as caterpillars feed on the leaves of specific host plants to complete their lifecycle. Birds often incorporate plant materials like milkweed fluff and other soft fibers to insulate their nests, and many songbirds rely on dried seed heads and late-season berries from herbaceous plants as a source of food. Native bees, such as leafcutter bees, use plant foliage to build individual cells inside hollow stems when laying their eggs in spring. These same hollow stems provide winter shelter until the adult bees emerge the following spring. Ground-nesting bees, as well as many butterflies and moths, benefit from undisturbed leaf litter, which offers both insulation and refuge during the winter months.
Practices like leaving leaf litter, hollow stems, and spent seed heads in the garden are valuable for promoting stewardship in home landscapes. However, if left unchecked, these practices can result in a wild, unmanaged appearance. By using them thoughtfully, home gardeners can create landscapes that support wildlife while also maintaining a tidy, aesthetically pleasing look.
Instead of shredding all leaf litter in the fall and removing it from the landscape, consider blowing or raking it into garden beds to serve as organic mulch. If you prefer the look of bark mulch, limit leaf mulch to areas with less public exposure, or consider leaving bark mulch at the front of planting beds, and using leaves towards the back. Maintaining clean marked paths can also aid in the perception of order. If thinning leaves in the spring is necessary, wait until late spring to ensure the successful emergence of insects overwintering in the litter.
To support insects utilizing hollow stems and cavities, leave a select number of stems standing through winter. In the spring, trim stems to varying heights between 8 and 24 inches. New growth will soon camouflage the cut stems. The following spring, cut back dead stalks from the previous season to varying heights, continuing the cycle. These approaches amplify the benefits to insects while also allowing gardeners to selectively groom landscapes for a managed aesthetic.
Pest Management
Choosing species and cultivars that are well suited to the environment as well as ones that possess genetic resistance against some of the most common pests and diseases is essential. Proper moisture and fertility management further sustains their good health. As discussed in Chapter 14, scouting and determining the best method of pest control is also essential. The gardener’s own threshold for pest damage will determine when control is needed. Some action could be required for diseases and pests that can cause long-term damage to the plants, but it is important to know which pests lead only to cosmetic damage. In these instances, a little extra patience can reduce the need for control actions and potentially maintain the ecological balance of the pests and beneficial insects in the landscape, so it is wise not to dash into the garden with insecticide sprays too quickly.
Summary
Herbaceous ornamentals help us accomplish landscape design goals, providing beauty and function as well as providing support to pollinators and other members of the ecosystem. Improve chances of success by developing an understanding of site conditions and selecting appropriate and well-adapted plants. Proper management of soil, water, and pests are also important elements of stewardship in gardens and landscapes.