Authors:
- Patrick Sweatt, Former Extension Agent, Tennessee State University
- Natalie Bumgarner, Associate Professor & Extension Specialist, University of Tennessee
Introduction
Weed management is a challenge that all Tennessee gardeners and homeowners face, whether in lawns, ornamental plantings, or vegetable and fruit plantings. Understanding the nature of weed life cycles and growth is an essential first step in developing an effective management plan, which must then be continually adapted to meet the needs of the season and crop.
Extension Master Gardeners are frequently asked to identify and prescribe treatments for many different types of weeds. This chapter first defines and classifies weeds according to their growth habit and then examines cultural, mechanical, and chemical methods for control. Understanding weed types and their characteristics and knowing how management recommendations must be adjusted to various environments are essential in helping gardeners and homeowners address weed problems.
What Is a Weed?
Definitions
Weeds can be defined in many ways, and not all scientists agree on a single description. However, the various definitions commonly include three distinct characteristics of a plant:
- Location: Is the plant growing outside of its normal habitat?
- Growth: What is the plant’s rate of spread and degree of success in competing with other plants in the area?
- Interference: What impact does the plant have on the people who manage the land where it is growing?
Definitions of weeds can range from the technical to the poetic. They can focus on agronomic or ecological aspects, as demonstrated in the following quotes:
- “A plant that is not valued where it is growing and is usually of vigorous growth; especially one that tends to overgrow or choke out more desirable plants.” —Merriam-Webster dictionary
- “A plant out of place … ” — Dr. William James Beal, Professor, Michigan State University
- “Plants that are competitive, persistent, and pernicious. They interfere with human activities and as a result, are undesirable.” —Applied Weed Science, by M. A. Ross and C. A. Lembi
- “A plant whose virtues have not yet been discovered … ” — Ralph Waldo Emerson
- “A plant that originated in a natural environment, and in response to imposed or natural environments evolved and continues to do so as an interfering associate with our crops and activities.”— R. J. Aldrich, Professor, University of Missouri
Sometimes, a US government agency defines and mandates action against a particular plant because of its competitive properties or its nature of interference. Such an action falls under the authority of Executive Order 13112, signed by the President in 1999, which establishes control over the introduction of “invasive species” or “alien invaders.”
In short, any plant may be considered a weed; it just depends on where it grows and what it impedes. It is important to recognize in many of these definitions the role of humans in determining what is or is not classified as a weed.
General Characteristics of Weeds
According to Robert L. Zimdahl, author of Fundamentals of Weed Science (4th edition, 2013), weeds generally exhibit these characteristics:
- rapid growth of seedlings and early reproduction ability (rapid maturation)
- multiple modes of reproduction by seed, by vegetative structures, or both
- often self-compatible or pollination is nonspecialized
- exhibit a range of seed strategies including lack of environmental requirements to germinate, varied dormancy, resistant to decay, multiple seed crops per year, size and shape similar to crop seeds, many seeds produced, and effective dispersal mechanisms
- roots that are able to grow deep, quickly, or have long-term reserves, allowing them to survive drought and heat stress
- adaptations that resist animal grazing, such as bitterness and thorns
- competitive advantages in obtaining water, nutrients, light, and other needs
- adaptable in terms of environmental conditions
- resistant to control strategies, which can include becoming resistant to herbicides
Negative Impacts of Weeds
Plants that are classified in an area as weeds are clearly a problem, but often for differing reasons. In addition to competing with desired plants for resources like sunlight, water, and soil nutrients, weeds can have other negative impacts. Weeds can affect crop productivity by increasing production, protection, and processing costs. Weed impacts can also negatively affect animal agriculture by reducing the quality and quantity of forage and hay production. While these losses are primarily related to commercial agriculture, weeds can affect the gardener and homeowner in many ways as well. The following sections present examples of various ways that weeds can cause losses and other concerns.
Weeds Can Serve as Hosts for Viral, Fungal, or Insect Pests
Black nightshade (Solanum nigrum) serves as an alternate host for late blight (Phytophthora infestans). Note that nightshade is in the Solanaceae family, which is the same as the tomato and potato, so there is a threat of this weed serving as an alternate host for pests of these important crop plants.
Insect pests are generally more prevalent in areas where weeds are not controlled. It is well documented that black cutworm moths (Agrotis ipsilon Hufnagel) are attracted to overwintering weeds such as annual bluegrass (Poa annua), yellow rocket (Capsella bursa-pastoris), and curly dock (Rumex crispus).
Jimsonweed (Datura stramonium) is a host plant for whiteflies that vector the viral disease tomato yellow leaf curl virus.
Weeds Can Interfere with Transportation or Infrastructure
The tree of heaven (Ailanthus altissima) can actually grow through cracks in asphalt or concrete.
Weeds Can Interfere with Aesthetics, Recreation, and Land Value and Use
Kudzu (Pueraria montana var. lobata) grows aggressively and often outcompetes trees by growing over them and robbing them of much-needed sunlight.
Weeds Can Lead to Allergies and Can Even Poison Humans or Pets
Ragweed (Ambrosia sp.) is a common cause of allergies in many areas.
The compound urushiol exuded by poison ivy (Toxicodendron radicans) is famous for its ability to cause contact dermatitis in sensitive people.
Jimsonweed (Datura stramonium) seeds contain high levels of the anesthetic atropine, which can cause death if ingested. (See photograph on page 15-19.)
Weed Classifications
Taxonomic Classifications
Weeds are generally classified as a broadleaf plant, a grass, or a sedge (see below).Broadleaf weeds are also referred to as dicots (dicotyledons) because they initially produce two leaves (cotyledons) following germination. (See Chapter 3.) Grass weeds are often referred to as monocots (monocotyledons) because they produce only one leaf at germination. Sedges are monocots that can look very similar to grasses, but they can be distinguished by their glossy leaf texture and triangular stems.
Life-Cycle Classifications
Weeds can also be further classified by their life cycle. Annual weeds reproduce from seeds and complete their life cycle within one year. Biennial weeds reproduce from seeds and complete their life cycle in portions of two years. Perennial weeds can continue to reproduce over a number of years by producing specialized aboveground or underground reproductive structures (such as rhizomes, tubers, and stolons) in addition to seeds. These structures make perennial weeds very difficult to control.
It is highly important to identify weeds correctly in the garden or landscape because control measures may vary, depending on the species present. Visit the University of Tennessee Turf Weed Identification Guide online to find pictures of many of the weeds listed in Tables 1 and 2 appearing on pages 15-17 and 15-18.
What is an Invasive Species?
According to the USDA, an invasive species is a nonnative to a particular ecosystem whose introduction causes or is likely to cause economic or environmental damage or harm to human health. Invasive plant species can generate many potential agricultural and ecological costs. However, only a small percentage of nonnative species become invasive. It is also possible for native species to act invasive because of changes in land use or other environmental changes, but the threat is often lower than that of nonnatives.
Actions taken to deal with an invasive species should be based on the extent of our ability to prevent, detect early, and control the threat; the extent of ecological damage it may cause; the economic importance of the crop; the costs of managing the invasion; and whether suitable replacement plants exist. It is the responsibility of Extension Master Gardener volunteers to respond to invasive species in the context of research-based information and in coordination with UT Extension personnel and procedures.
Examples of invasive plants listed as a severe threat in Tennessee include the tree of heaven (Ailanthus altissima), mimosa (Albizia julibrissin), Asian bittersweet (Celastrus orbiculatus), Chinese privet (Ligustrum sinense) (see adjacent page), autumn olive (Elaeagnus umbellata), kudzu (Pueraria montana var. lobata) (see adjacent page), empress tree (Paulownia tomentosa), multiflora rose (Rosa multiflora), purple loosestrife (Lythrum salicaria), and Japanese honeysuckle (Lonicera japonica). Additional information on these and other species can be found at the Tennessee Invasive Plant Council website tnipc.com.
Cultural and Mechanical Weed Control
Weeds may be controlled in several effective ways; however, many of the techniques outlined in this section are not standalone methods for long-term weed control. Effective long-term weed control programs integrate multiple techniques, such as the cultural and mechanical practices discussed in this section. In many ways, the following practices should be seen as simply “good gardening techniques” that should be practiced as a matter of course, practices that can be effective whether or not chemical controls are considered.
Sanitation
Sanitation is the act of inspecting plant materials, soil, or seeds before introducing them to a garden or landscape area. This technique helps prevent the introduction of seeds or other reproductive structures of undesired plant species to the garden or ornamental beds. Sanitation may also include sterilizing soils or other growing media to destroy the viability of weed seeds.
Sanitation techniques may be effective in preventing the introduction of several weed species; however, it is extremely difficult to identify and remove or destroy all reproductive structures of all weed species. As a result, sanitation should be considered a necessary step in reducing the risk of introducing the most aggressive and persistent weed species.
Teach clients to inspect the soil, seeds, and roots for weeds and weed reproductive structures (such as stolons and rhizomes) before transplanting any potted plant or adding topsoil or organic amendments that may contain weed structures. If weeds or their reproductive structures are found, they should be carefully removed by hand or by rinsing them gently with running water. Reproductive structures should be rinsed off away from bedding areas and lawns, where they could later germinate.
Planting Practices
Row spacing is one of the most often overlooked methods for reducing weed competition in vegetable crops. One example is the use of double or triple rows. Crops such as beets, radishes, or leaf lettuce can be planted closely in multiple rows to enable their leaves to cover the soil more quickly. Covering bare soil by crops is referred to as canopy closure and is a very effective way to reduce the competitiveness of germinated weeds by blocking sunlight. Never space vegetable crops further apart than is recommended. Doing so can lead to areas of exposed soil that are larger than necessary, thereby increasing weed management challenges. Conversely, perennial crops should not be spaced closer than is optimum to cover the area quickly because over time plant productivity and health can be limited by crowding.
Another example of using planting techniques to reduce weed pressures is to rotate the desired crops with cover crops, such as rye grasses or buckwheat. Cover crops can also be used before installing an ornamental planting area to improve soil quality (see Chapter 6) and reduce weed pressures. Cover crops can reduce weed pressure by smothering, or quickly forming a thick cover, to prevent weed germination. Some cover crops can also produce substances that prevent weed seed germination.
Cultivation
Cultivation is the practice of mechanically disturbing the soil in order to uproot weeds. Uprooting weeds allows them to desiccate (dry out) in the sunlight. In gardens and ornamental beds, cultivation is often done with a hoe or a rotary tiller. Cultivation may be done before planting or selectively between rows of emerged crops or ornamental plants. In general, cultivation is highly effective in controlling most annual weeds, but it can sometimes aid in the spread of perennial weeds by spreading smaller fragments of the underground reproductive structures. Tilling can also bring weed seeds to the surface that were buried and prevented from germinating. Therefore, the life cycle of the weeds and potential seeds present in soil should be determined before any control measures are undertaken.
In turf, cultivation is done with either a solid- or hollow-tine aerator. Cultivation in turf usually improves internal drainage, which can subsequently discourage some weed species that prefer compacted, poorly drained soils (such as goosegrass and sedges). Weed pressures can be reduced both by improving conditions for desirable turfgrass species and hindering weed growth that prefers compacted conditions.
Managing Perennial Weeds with Cultivation
When managing perennial weeds with cultivation it is important to follow a few rules:
- Attempt to remove as much of the perennial root structure as possible from the soil.
- Minimize the spread of these perennial structures to other parts of your garden or ornamental beds. Use care to avoid carrying reproductive structures on tiller tines or other tools to those areas.
- Wait about one or two weeks after perennial weeds have emerged before initiating any type of cultivation. Continue cultivation at these intervals until the weed is effectively removed from the area. If the problem does not improve, treatment with a systemic herbicide may be necessary for optimal control.
Mulching
Mulching is the act of smothering or preventing light from reaching weeds. If a weed does not receive light, plant photosynthesis and growth are inhibited. Many weed seeds also require light for germination. Mulches are most often differentiated by whether they are organic or inorganic. Organic here refers to a material that was previously living. It does not refer to being certified organic by the USDA. Organic mulches include materials that were derived from previously living matter, such as grass clippings, manure, straw, ground tree bark, sawdust, wood chips, rice or peanut hulls, compost, leaves or pine needles, and newspapers. Organic mulches provide benefits other than weed control because they add organic material to soils.
Unfortunately, organic mulches are less effective at inhibiting the growth of perennial weeds that are able to push through these barriers with the energy stored in their underground reproductive structures. Organic mulches may also harbor insect pests or diseases that can create unforeseen issues in the garden or ornamental beds.
Inorganic mulches include plastic films, woven fabrics, shredded rubber, and other materials not derived from living matter. Plastic films and woven fabrics are effective in controlling both annual and perennial weeds with the exception of certain perennials that are able to penetrate some types of mulch, especially if any holes are present. (See sedge photograph page 15-7.)
Woven fabrics have the added benefit of allowing water to permeate their surface, which enhances the ability of the user to maintain even watering when compared with the impermeable surface of plastic films. However, woven fabrics may allow certain weeds to germinate on their surface, which is not generally an issue with plastic films. Herbicides impregnated on or applied in conjunction with woven fabrics will improve weed control when used appropriately.
Inorganic mulches are much more common in the vegetable garden because they are applied temporarily. Plastic mulches, both solid and woven, can create issues when used for longer durations in landscape beds. Solid plastic in ornamental beds restricts water and air movement, and woven fabrics can make weed removal challenging. Specific uses of organic and inorganic mulches for vegetable gardening, home fruit production, and in ornamental landscapes are discussed in chapters 11, 12, and 8, respectively.
Soil Solarization
Solarization can be used in preparation for a variety of crops including ornamental beds, vegetable gardens, or even fruit production areas. Solarization methods include the use of clear plastic to trap solar radiation and heat up the soil under the plastic to kill weed seeds. By increasing soil temperatures up to 120 or 130°F, most weeds and weed seeds can be killed, but it is necessary to leave the plastic in place four to eight weeks to ensure that high enough temperatures have been reached. Keep in mind that this treatment will typically be most effective for weed seeds in the top 2 to 3 inches of soil. Do not till deeply after solarization; otherwise, viable seeds from cooler soil depths will be brought to the surface. Many fungal and bacterial diseases can also be reduced by solarization. In order for solarization to be fully effective, several steps must be taken.
First, in Tennessee it is necessary to have a summer fallow period because temperatures under the plastic will not be high enough for the process to work well in spring or fall. In fact, even some summer seasons in northern and eastern parts of the state may not maintain the daytime and nighttime temperatures required to effectively solarize soil.
Second, make sure the soil is bare and moist. The heat needed for solarization is better transferred through wet soil than dry soil.
Third, select clear plastic that can withstand four to eight weeks outdoors without degrading. Plastic that is UV stabilized works well, but less durable painter’s plastics may last long enough to be effective. Remove the plastic before it degrades too much or the pieces will be quite difficult to collect.
One or two layers of plastic can be installed over the area to be treated. A double layer of plastic reduces nighttime temperature losses because the air between the layers serves as an insulator. Use foam or wood spacers to separate the two layers of plastic several inches from each other and from the soil. The edges of the plastic sheets should be tightly held down by soil. Keep the plastic as clean as possible to maximize light penetration.
Flame Cultivation
Flame cultivation with a propane-powered flamer is gaining acceptance as a method of weed control, even in larger commercial operations. Flame cultivation uses propane “‘torches” to burn and rupture the photosynthesizing structures of weed leaves with heat, causing them to die. It has been demonstrated to be safe and effective for weed control in both row and vegetable crops. The size of weeds at the time of flame application as well as the leaf cuticle size directly affects the level of weed control obtained with flame cultivation. Larger weeds are less affected by flame and can be more difficult to manage with this method. However, larger weeds and larger leaf cuticle sizes are harder to control in general. When used properly, flame cultivation has performed better than certain pesticides, especially when multiple flame cultivations were made to a specific area.
Tips for controlling weeds with a single-orifice, propane-powered flamer are:
- target applications to weeds when they reach 2 to 3 inches in height
- do not linger for multiple seconds on individual weeds but move briskly over the tops of the weeds with the flamer. The flame can very quickly boil the water in each plant, causing rapid tissue necrosis
- plan to flame secondary flushes of weeds or regrowth of grasses or perennial broadleaf weeds approximately two to four weeks after your initial application
- avoid contacting the foliage of desirable plants with any part of the flame
- make flame applications during hot and dry periods for maximum efficacy; just be sure to have a water hose on hand.
Mowing
Mowing is the process of killing a plant or impairing its growth by cutting. Often the word mow brings to mind lawn maintenance, but mowing can include equipment other than lawnmowers and can include plants other than turfgrass. Any time a hedge is pruned with clippers, a bush or tall grass is cleared with a scythe or machete, or a tree is cut down with a chainsaw, a type of mowing is being performed.
Mowing is an extremely effective way of controlling erect, growing, annual broadleaf weeds. However, prostrate-growing broadleaf weeds can often escape the cutting blades of a lawnmower by growing laterally across the soil surface. Grass and sedge weeds are suppressed but rarely controlled completely by mowing. In addition, the top-growth of perennial broadleaf weeds and brush or tree species may be effectively removed by mowing, but regrowth from rich reserves in their perennial root structures often occurs.
Hand Weeding
Hand weeding is the oldest and one of the most effective methods of weed control. Annual grasses, broadleaf, and sedge weeds can all be controlled by this method. To successfully control a perennial weed through hand weeding, the entire underground reproductive system must be removed. Hand weeding is especially effective in controlling weeds next to plants where hoeing or other forms of cultivation would cause excessive damage. When hand weeding, wear appropriate gloves, as some plants have physical and chemical defense mechanisms that can cause discomfort or harm to humans.
Chemical Weed Control
Herbicides are chemicals that kill plants or suppress their growth. Hundreds of chemicals are used as herbicides throughout the world. They can be classified by their (1) mode (or site) of action, (2) timing of application, (3) selective or nonselective activity, (4) systemic, contact, or residual activity, and (5) synthetic or nonsynthetic origin. Nonsynthetic refers to materials that were derived from natural sources, but may not necessarily mean allowable in USDA certified organic systems. Keep in mind that there can be some overlap in these categories, and a single weed control material can be described by multiple descriptors.
It is essential to recommend to homeowners and gardeners only those products that are labeled and appropriate for their crop in home lawns, gardens, and landscapes. Always provide UT Extension publication recommendations, and never give any suggestions that do not comply with Tennessee Extension recommendations and the label on the product.
Mode and Site of Action
Mode of action describes the specific activity on a physiological process in plants (for example, glyphosate prevents the formation of aromatic amino acids in plants), whereas an herbicide’s site of action describes the specific biochemical target interfered with by the herbicide (for example, glyphosate inhibits the enzyme 5-enol-pyruvyl-shikimate-3-phosphate synthase or EPSP synthase). In general, the mode of action is known for most commercial herbicides. However, the site of action is not always known. It is not crucial for gardeners and homeowners to understand the chemistry and physiology of the herbicide. However, it is important to understand that repeatedly using products with the same mode of action can lead to resistance in weeds. Whenever possible, products should be alternated to reduce this possibility.
Timing of Application
Herbicides must be applied at the proper time to provide optimal weed control while minimizing any possible negative response in desired plantings. Herbicides can be grouped by their timing of application. Most often these are known as preemergence or postemergence herbicides.
Preemergence applications are made prior to the emergence of the weeds or plants of interest. In contrast, postemergence applications are made after the emergence of weeds or plants of interest. Other herbicide application timings include preplant, postdirected, and spot spray.
- Preplant herbicide applications are made before planting the plants of interest and, in general, are made to “burn down” existing weed vegetation before planting.
- Postdirected applications are directed to the base of plants in a way that prevents or minimizes contact of the spray solution on the foliage. Extreme care must be taken when applying an herbicide in this manner, as small amounts of a fine spray can drift and cause damage to crops.
- Spot spray treatments are often made with a set amount of herbicide dissolved in a spray solution that is applied to the foliage of small, intermittent patches of weeds in a field.
Other considerations may include temperature, time of day, preharvest interval (PHI), and plant-back restrictions for each specific chemical. The PHI defines the waiting period necessary before consuming (eating) plant material, whereas plant back restrictions quantify the time that should be allowed before new plantings are carried out. Always consult and comply with the herbicide label because it represents the legal use of the product.
Selective Versus Nonselective Herbicides
Herbicides are also classified by whether their activity is considered selective or nonselective. A selective herbicide controls certain weeds but will not cause injury to a desired plant if applied at the correct rate. Most herbicides are sold for selective weed control. Certain plants are generally tolerant to these selective herbicides because they are able to compartmentalize, exude, or metabolize the herbicide so that it is no longer a threat.
Herbicides might be selective or nonselective based on the manner of application. For example, the herbicide trifluralin can be applied postemergence over the top of watermelons without injuring this plant. However, if applied preemergence, severe watermelon injury may occur.
In contrast to selective herbicides, a nonselective herbicide will cause damage to most any plant material that it contacts. Glyphosate, paraquat, diquat, glufosinate, imazapyr, and pelargonic acid are examples of herbicide active ingredients that are considered to be nonselective. These materials should be used with extreme caution when spraying around desirable vegetation.
Systemic, Contact, and Residual Herbicides
Herbicides can also be classified by how they enter the plant and how they behave once they come in contact with plant tissue or soil. Systemic herbicides enter plants and move freely within its tissues. In general, systemic herbicides are better at controlling larger weeds and generally take longer to show physical damage because of their extensive movement in plants. This delay is especially likely to be observed with perennial weeds, in which systemic herbicides are able to accumulate to toxic levels in the underground reproductive structures. Glyphosate and imazapyr are examples of commonly used systemic herbicides that are absorbed through foliage and translocated to root and shoot growing points, or meristems.
In contrast, contact herbicides control only the portion of the plant that the spray solution covers. Diquat and pelargonic acid are examples of commonly used contact herbicides.
Residual herbicides are able to enter plants through the roots or emerging shoots in the soil profile. They must be “activated” by shallow incorporation or with approximately 1/2 inch of rainfall or overhead irrigation. Preemergence herbicides, which have residual activity, create barriers that prevent the survival of germinating weed seedlings. Contrary to popular belief, these herbicides do not prevent seed germination; instead, they prevent maturation of the weeds by inhibiting growth processes in these plants. Most contact herbicides (such as glyphosate) are not residual herbicides, but some systemic herbicides actually do have residual activity in the soil (for example, imazapyr). There are many residual herbicides (such as trifluralin) that have little to no contact or systemic activity when applied to the foliage of weeds.
Synthetic Versus Nonsynthetic Herbicides
Nonsynthetic herbicide materials are those derived from natural sources rather than industrial processes. Many of these herbicides are allowable for certified organic production, but they should be individually checked against allowable materials lists to be certain. The Organic Materials Review Institute (OMRI) provides such lists of allowable materials.
Many nonsynthetic herbicides provide postemergence, nonselective, contact weed control. Examples include clove oil, vinegar, lime or lemon juice, and cinnamon oil. Clove oil and cinnamon oil contain the herbicidal chemical eugenol, while vinegar’s herbicidal agent is acetic acid. Citric acid is the herbicide in lemon and lime juice and can be natural or created synthetically. Currently, the only preemergence residual herbicide for organic production is corn gluten meal. A combination of dipeptides (proteins) present in corn gluten meal is the basis for its herbicidal activity.
Commonly Used Herbicides
Currently, there are only a few herbicides available for use in home gardens and ornamental beds. It is also important for gardeners and homeowners to understand that some herbicides are selective for monocots or dicots, so correct weed identification is a crucial first step for control. The reason for such limited options is that few herbicides can actually control a diversity of weeds while maintaining selectivity to a wide array of desirable plants. A list of most herbicides available for use in home gardens and ornamental beds can be found in UT Extension publications provided in the digital companion section for this chapter.
Before a gardener uses any of these products, he or she needs to consult the product label for specific instructions for proper use in the area. Special attention needs to be paid to the formulation, use rate, mixing instructions, and specific uses allowed for the specific product. The label is the law, and herbicide products are regulated by both federal and state guidelines, with special emphasis on safety to the herbicide applicator, the consumer, and the environment. By following the label exactly as directed, gardeners can safely combat weeds.
Gardeners should never rely solely on trade names for any pesticide product. Companies that produce pesticides change the ratios and the types of active ingredients in their products often, so similar product names may not indicate the same product that has been used previously. Always search for the proper product by the common name of the active ingredient.
Summary
Plants become weeds when they interfere with the goals of land and waterway managers, producers, and gardeners. To control weeds properly, accurate identification is essential so that the correct control measures can be chosen. Often, programs that incorporate several of the techniques outlined in this chapter offer the best chance of managing weed pressure.
At the heart of effective weed management is a commitment to prompt response. Weeds that are allowed to grow until they cannot reasonably be controlled or that have set seed have been left too long. Through the use of proper identification, diverse management methods, and appropriate controls, Extension Master Gardeners should be able to respond appropriately to a range of weed questions and issues.
Most Common Garden Weeds in Tennessee
Broadleaf Weeds
| Common Name | Scientific Name | Life-Cycle Classification |
|---|---|---|
| Redroot Pigweed | Amaranthus retroflexus | Annual |
| Common ragweed | Ambrosia artemisiifolia | Annual |
| Hairy bittercress | Cardamine hirsuta | Annual |
| Common lambsquarters | Chenopodium album | Annual |
| Jimsonweed | Datura stramonium | Annual |
| Prostrate spurge | Euphorbia (Chamaesyce) humistrata | Annual |
| Hairy galinsoga | Galinsoga ciliata | Annual |
| Morning glory species | Ipomoea spp. | Annual or perennial |
| Henbit | Lamium amplexicaule | Annual or perennial |
| Purple deadnettle | Lamium purpureum | Annual |
| Carpetweed | Mollugo verticillata | Annual |
| Yellow woodsorrel | Oxalis stricta | Annual or perennial |
| Common purslane | Portulaca oleracea | Annual |
| Buttercup species | Ranunculus spp. | Annual |
| Common chickweed | Stellaria media | Annual |
| Dandelion | Taraxacum officinale | Annual or perennial |
Grasses and Sedges
| Common Name | Scientific Name | Life-Cycle Classification |
|---|---|---|
| Bermudagrass | Cynodon dactylon | Perennial |
| Yellow nutsedge | Cyperus esculentus | Perennial |
| Large crabgrass | Digitaria sanguinalis | Annual |
| Goosegrass | Eleusine indica | Annual |
| Barnyardgrass | Echinochloa crus-galli | Annual |
| Annual bluegrass | Poa annua | Annual |
| Dallisgrass | Paspalum dilatatum | Perennial |
| Foxtail species | Setaria spp. | Annual or perennial |
| Johnsongrass | Sorghum halepense | Perennial |
Most Common Turf Weeds in Tennessee
Broadleaf Weeds
| Common Name | Scientific Name | Life-Cycle Classification |
|---|---|---|
| Virginia buttonweed | Diodia virginiana | Perennial |
| Prostrate spurge | Euphorbia (Chamaesyce) humistrata | Annual |
| Ground ivy | Glechoma hederacea | Annual |
| Henbit | Lamium amplexicaule | Annual or perennial |
| Purple deadnettle | Lamium purpureum | Annual |
| Yellow woodsorrel | Oxalis stricta | Annual or perennial |
| Broadleaf plantain | Plantago major | Perennial |
| Buckhorn plantain | Plantago lanceolata | Perennial |
| Prostrate knotweed | Polygonum aviculare | Annual |
| Common purslane | Portulaca oleracea | Annual |
| Common chickweed | Stellaria media | Annual |
| Dandelion | Taraxacum officinale | Annual or perennial |
| White clover | Trifolium repens | Perennial |
| Wild violet | Viola papilionacea | Perennial |
Allium Family
| Common Name | Scientific Name | Life-Cycle Classification |
|---|---|---|
| Wild garlic | Allium vineale | Perennial |
Grasses and Sedges
| Common Name | Scientific Name | Life-Cycle Classification |
|---|---|---|
| Bermudagrass | Cynodon dactylon | Perennial |
| Yellow nutsedge | Cyperus esculentus | Perennial |
| Large crabgrass | Digitaria sanguinalis | Annual |
| Smooth crabgrass | Digitaria ischaemum | Annual |
| Goosegrass | Eleusine indica | Annual |
| Barnyardgrass | Echinochloa crus-galli | Annual |
| Green kyllinga | Kyllinga brevifolia | Perennial |
| False green kyllinga | Kyllinga gracillima | Perennial |
| Nimblewill | Muhlenbergia shreberi | Perennial |
| Annual bluegrass | Poa annua | Annual |
| Dallisgrass | Paspalum dilatatum | Perennial |
| Foxtail species | Setaria spp. | Annual or perennial |
| Johnsongrass | Sorghum halepense | Perennial |