examples of biennial weeds

Weeds can reduce crop yield, affect the aesthetic qualities of landscapes and the functionality of sports turf, and displace native flora in natural areas. By planting lettuce intensively instead of in single rows, weed growth is greatly reduced. There is a giant ragweed (Ambrosia tridida) which grows up to 14 high. We have been conditioned to think of weeds as pests to be eradicated from tidy landscapes. Once introduced to a site, weeds can spread rapidly, and they are remarkably persistent. Nutsedge can also be reduced by tilling and leaving the tubers exposed during the month of August when new tubers are normally formed. On-site sanitation is another effective cultural control method. 3. Leaves are generally narrow and upright with parallel veins. The Gardener's Weed Book: Earth-Safe Controls. A musk thistle in its flowering form. The majority of herbicides used are selective. Weeds of the Northeast. Avoid planting potentially invasive plants, or install some type of control. It is pinnately toothed, it can have 3 lobes, with the center lobe larger than the others. Germination occurs when soil temperatures consistently reach 55 degrees F and is generally killed at the first frost. Dandelions have many positive features, including these: Mechanical management is used to kill weeds directly or to make the environment unsuitable for them. North Adams, Massachusetts: Storey Publishing, 1996. This summer annual has alternate leaves. Cultural managementMulching prevents bermudagrass seedlings from establishing but will not prevent bermudagrass from reestablishing via rhizomes or stolons left in the soil. In addition, weeds that do germinate under mulch may die because they do not have enough stored energy in their seeds to enable them to grow through 3 inches of mulch to reach sunlight and produce leaves. Richards, Flickr You confirm the sample is that of bermudagrass, Cynodon dactylon. The Garden wouldn't be the Garden without Nutsedge, bermudagrass, quackgrass, and Canadian thistle do not lose their viability until their moisture content drops below 20%. State and federal laws regulate the presence of certain weed species in crop seeds. Winter wheat is a biennial plant that requires vernalization to produce grains. Number of seeds produced by select weeds. Most of the management strategies require removing the iris and then replanting once the bed is clear of bermudagrass. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status. Weeds sometimes attract or harbor harmful insects or serve as alternate hosts for plant pathogens. There will still be crabgrass seed in the soil and the herbicide can prevent further infestation. Bradley. It is covered with hairs. Leaves are diverse but generally broad with netted veins. It has a slightly bitter taste and it has no scent. Chemical management of weeds relies on the use of herbicides. Examples of biennial plants are members of the onion family including leek, [4] some members of the cabbage family, [4] common mullein, parsley, fennel, [4] Lunaria, silverbeet, black-eyed Susan, sweet William, colic weed, carrot, [4] and some hollyhocks. Rushes have rounded, hollow stems (Figure 610), and their leaf blades are round in cross section (grass and sedge leaf blades are flat). Yellow woodsorrel (Oxalis grandis), for example, has evolved a mechanism to forcefully expel its seeds up to 12 feet from the plant. CC BY-SA 4.0, F.D. Plantains, dandelion, and ground ivy are examples of perennial turf weeds. Summer annual weeds emerge in the spring or early summer, grow during the summer, produce seed in mid to late summer, and are killed by frost in the fall. Barnyardgrass (Echinochloa crus-galli) is a summer annual grass that germinates from seeds from late winter or early spring throughout the summer. Other common biennial vegetables are Swiss chard, beets, Brussels sprouts, and kale. Pokeweed (Phytolacca americana) leaves are poisonous unless carefully prepared (harvest only young leaves and change the water when cooking). Acknowledgments. In: K.A. Emily May, Flickr Creeping, spreading-type bamboos are very weedy once established and are extremely difficult to control. In shady or irrigated landscapes or in cooler mountain regions, soil temperatures stay cool, allowing some winter annual weeds (such as chickweed) to germinate and grow during summer. Early-season growth of perennial weeds is rapidneither chemical nor mechanical controls are very effective. Both spurges reproduce from seed. It does well with heavy foot traffic and a hot dry climate, but it can easily become an invasive weed. Weed identification references are listed in the "For More Information" section at the end of this chapter. Auricles are absent. Tree roots often extend twice as far as the branches and may extend out beneath turf and be harmed by herbicides applied to lawns. Some common annual, biennial, and perennial weeds. These weeds will grow year after year unless you remove the whole root. If the soil does not receive adequate water in this time frame, the herbicide will not be activated and, therefore, weed control will generally be poor. In the first year seeds germinate and grow without flowering, forming what is called a rosette. For example, seeds of many summer weeds require some cold temperatures before they will germinate. Every part of the plant is edible. Remember that weeds can appear to be different from a picture when the weed has been mowed or has been growing under less than ideal conditions (such as shade or moisture stress). An example of a biennial weed that we see in the NRV would be musk thistles. It spreads by seed. (The following Weed ID pages linked to with permission of UMass Extension.). A 3- to 4-inch layer of mulch will help reduce weeds in planting beds. Dandelions thrive in sunny environments and can be found in the United States and Europe. Examples of biennial weeds include Queen Anne's lace (Daucus carota) and bull thistle (Cirsium vulgare). A musk thistle in its rosette form. Print. Examples include dandelion, plantain, dogfennel, and curly dock. CC BY 2.0. This quiescent state is referred to as dormancy. Example of biennial plants Carrots Broccoli Beets Kale Celery Cabbage Brussels sprout Parsley Dill Hardy, Half-hardy, and Tender Frequently, when it comes to classifying a plant into one of these categories based on its life span, you may also encounter terms like hardy, half-hardy, and tender. Fertilizer placed in bands near desired plants instead of broadcast widely helps the desired plants grow without promoting weeds. CC BY 2.0. Goosegrass can be identified by the whitish stems at the base that are extremely compressed and flattened. In all cases, effective weed management includes preventing reproduction by removing flowers before they can set seed. CC BY-SA 2.0, kenny_point, Flickr However, where kudzu grows, there is usually very little else growing. It roots at the nodes on the stems if they touch the ground. The label is the best reference on how to use an herbicide effectively and safely. As they emerge, dicot seedlings have two seed leaves. Mustard, watermelon, corn, lettuce wheat, are a few examples of annual plants. Those herbicides can negatively affect desirable plants when that compost containing herbicide residues is added (Figure 617). Preemergence herbicides remain effective for 6 to 12 weeks (varies with the chemical). Monocot WeedsMonocots typically have long, narrow leaf blades with parallel veins. The fruit is an achene, which resembles a queens crown. In addition to sexually reproducing by seeds, many weeds reproduce asexually via tubers, corms, bulbs, and stem and leaf rooting. Soil builds up behind the blade and moves weed seeds to the soil surface. Photo from VCE Weed Identification website. commitment to diversity. Other plants, however, may or may not be considered weeds depending on ones viewpoint. Dandelion Botanical name: Taraxacum officinale Category: Perennial broadleaf Size: 2-18 inches The examples include some of the most common weeds, as well as the most problematic. As with any rule, exceptions occur. A crabgrass plant which needs warm soils and sunlight can produce 150,000 seeds. Preemergence herbicides are not effective on bermudagrass from rhizomes or stolons but will control bermudagrass from seed. CC BY 2.0, Mcleay Grass Man, Flickr Puncturevine (Tribulus terrestris) is a summer annual weed with multiple stems prostrate along the ground. Prostrate spurge has inconspicuous small, pinkish white flowers in the leaf axils. Follow-up treatments with herbicides are usually required. If the bamboo is encroaching from an adjacent area, install a root-barrier 12 to 18 inches deep. Opposite leaves are egg-shaped in outline and once or twice compound (pinnatified), they are hairy on their upper surface and margin. Uva, Richard H., Joseph C. Neal, and Joseph M. DiTomaso. Systemic herbicides can also be classified as selective or nonselective. Bloom is in late spring and early summer. Barnyardgrass is found in moist soils, especially soils high in nutrients. This damage is completely avoidable if areas around the base of trees and shrubs are mulched and weeded by hand. North Central Regional Publication NCR281. The most reliable way to identify grasses is by their floral characteristics. For example, there are selective contact herbicides that can control yellow nutsedge in turfgrass. According to origin: Alien (foreign in origin): Argemone mexicana (Shialkata - Mexico), Eichhornia crassipes (Kachuripana - Germany). To be effective, herbicides must be applied at the proper time in relation to the growth stages of the weed and the desirable plant. Scot Nelson, Flickr How important is this particular planting bed? It is an example of use of the precautionary principle: . But if the debris is not fully composted, many weeds can be introduced to garden or landscape beds. All parts of jimsonweed (Datura stramonium) (Figure 61) contain toxic alkaloids that cause hallucinations, convulsions, or death; contact with jimsonweed sap causes a skin rash on some people. When the leaves of both spurges are broken or injured they emit a milky white sap (similar to dandelion). Use adapted plants and cultivars, maintain adequate soil fertility, plant at the proper date, and seed or plant at the correct depth and rate. CC BY 2.0, Harry Rose, Flickr The leaves are alternate, the seeds (1/25") are shiny, round and flat. Figure 63. 414, North Carolina Agricultural Chemicals Manual, NC State University TurfFiles Centere website, "Which Plant Type Do I Have?, NC State University TurfFiles Centere, Kathleen Moore, Urban Horticulturist, Department of Horticultural Science, Joe Neal, Extension Weed Specialist, Department of Horticultural Science, Lucy Bradley, Extension Specialist, Urban Horticulture, Department of Horticultural Science, Contributions by Extension Agents: Joanna Radford, Jessica Strickland, Susan Brown, Kelly Groves, Donna Teasley, Shawn Banks, Danelle Cutting, Contributions by Extension Master Gardener Volunteers: Jackie Weedon, Karen Damari, Connie Schultz, Kim Curlee, Lee Kapleau, Judy Bates, Chris Alberti, Content Editors: Lucy Bradley, Associate Professor and Extension Specialist, Urban Horticulture, NC State University; Director, NC State Extension Master Gardener program; Kathleen Moore, Urban Horticulturist. The seed pod turns black at maturity. Some plants that are especially sensitive to herbicides include grapes, tomatoes, elms, sycamores, petunias, roses, apples, dogwoods, redbuds, forsythias, and honey locusts. Option 1. Clean equipment after each use because weed seeds can be moved on rototillers and mowers. For example, if flowers are planted close enough that they grow to touch the adjoining plant, weeds have less room and light to grow. As a result, it can take years to reduce the weed seed "reserve" already existing in the soil. Regardless of their other qualities, by definition all weeds are plants growing where they are unwanted. Also, check container-grown and balled-and-burlapped plants for weeds before purchasing or planting; pay particular attention to perennial weeds such as nutsedge, bindweed, and bermudagrass. It germinates when soil temperatures reach 65 degrees. It does last 2-3 hours then the petals drop. Trumpet creeper (Campsis radicans), for example, is a perennial woody vine that has beautiful flowers but also an ability to self-seed. Gorse seed has been known to last for at least 20 years in the soil. A benefit to using biological management versus broad-spectrum herbicides is its relative safety and low impact on the environment. Emerged weeds can be burned by a flame weeder or an herbicide (natural or. Jerusalem artichokes should be planted only in an isolated area, with precautions taken to prevent the spread of roots, rhizomes, and tubers. Herbicides can also carry over in manure. Prostrate spurge roots at the nodes, but spotted spurge does not. One of the easiest ways to distinguish between yellow and purple nutsedge is to look at the leaf tip. Preemergence herbicides are effective in controlling most annual grasses and some small-seeded broadleaf weeds. Youth, Community, and Therapeutic Gardening, Appendix B. Each leaflet is less than inch long. Nonselective herbicides must be applied in a manner that avoids contact with desirable plants. The perennial sedgespurple nutsedge, yellow nutsedge, and kyllingaare particularly difficult to control. Perennial Weeds Perennial weeds live for multiple years and do not die after flowering. For example, nutsedge tubers planted one every square foot on an acre of land can produce over 3 million plants and 4 million tubers in one season. This may need to be repeated several times throughout the summer. High temperatures (85F or above) cause some herbicides to volatilize and move as an invisible gas to nontargeted plants and can cause excessive burn to plants in the treated area. Possible poisoning cases should be referred to the nearest Poison Control Center. Avoid contact with desirable vegetation or the grass. If you desire to plant bamboo in the landscape, hedge bamboo (Bambusa multiplex) is a tall, tightly clumping bamboo species that can be grown in our area. The ligule is a short fringe of hairs and the auricles are absent. Sometimes it is confused with Johnson grass or barnyard grass, but fall panicum has a hairy ligule. Annual Plants Examples. According to the growing season: Photo from VCE Weed Identification website. Apophytes (Indigenous to a country - Bangladesh): Oryza sativa var. Culms are erect or spreading at the base. Remember bermudagrass rhizomes may grow 6 to 8 inches deep. The flowers, which consist of 5 petals, produce hard, spiny, five-lobed fruit. Identify the desirable plants to be protected and the problem weeds to be killed. Print. Some winters are very mild or have fluctuating temperatures. There are also some pre-emergent herbicides available which form a chemical barrier in the soil and prevent the weeds from emerging. Biennials. Mechanical methods include selectively excluding weeds, creating barriers, and such practices as hoeing, cultivating, mowing, and pruning. A pre-emergent herbicide is recommended even if some crabgrass plants have germinated. Whenever a garden is cultivated, the site is essentially disturbed, which allows natural succession processes to start over again and again. Black medic (Medicago lupulina) is a summer annual that can act as a perennial. Goosegrass can tolerate heavy traffic, dry compacted soils and low mowing heights. Kathleen Moore This article was last updated on 07/20/22 Spotted spurge has a more erect growth habit than prostrate spurge. AG-831. Figure 618. The ligule is toothed and membranous with a cut in the center. Skip to Weed Management: The Integrated Pest Management (IPM) Approach, Skip to Case StudyThink IPM: Grass in a Flower Bed, North Carolina Extension Gardener Handbook, NC State Extension Gardener Plant Toolbox, Plants Poisonous to Livestock and Pets in North Carolina, Center for Invasive Species and Ecosystem Health, Diagnosing Herbicide Injury on Garden and Landscape Plants, Purdue University, Diagnosing and Preventing Herbicide Injury to Trees, by Bartlett Tree Research Laboratories, Herbicide Injury in the Nursery and Landscape, by Oklahoma State University, Perennial & Biennial Weed Guide, by Ohio State University, Plant Injury due to turfgrass broadleaf weed herbicides, University of Wisconsin, Turfgrass Weeds, by University of Tennessee, Weed Control Methods Handbook, Utah State University, Weed Identification Guide, by Virginia Tech, Weed Management in Nurseries, Landscapes & Christmas Trees, 21. Because nonselective herbicides indiscriminately control all plants, use them only to kill plants before renovating and planting an area, as a spot treatment (avoiding contact with desirable plants), or on a driveway or sidewalk where no vegetation is the desired end result. Edible weeds can be enjoyed in a variety of ways. There are two types of annual weeds. Occasionally, if conditions are harsh, biennial plants will act like annuals and flower during their first year. Nonselective herbicides control or kill green plants regardless of species, controlling or damaging almost any plant contacted by the spray. The dispersal of these seeds is one of the great milestones of childhood. The flower is a dense terminal spike 1-8 long, usually ascending. Purchase and maintain proper herbicide application equipment. H. trionum is grown in Europe as an ornamental. And weed seeds can be in the root balls of purchased plants (Figure 66). Consequently, the presence of certain weeds may be used as an indicator of soil or management problems that need to be addressed. The difference is in the flower. Publication MP 169. This is a classic case of a hardy annual that performs better when treated as a biennial. N.C. The collar is narrow and continuous. Prostrate spurge (Euphorbia supine) and spotted spurge (Euphorbia maculate) are summer annual weeds. It is an annual crop with an average lifespan of 4 - 8 months. Weeds of Arkansas Lawns, Turf, Roadsides, Recreation Areas: A Guide to Identification. Lists of weeds that herbicides control and which plants they can be safely used on are included in NC State Extension publications such as the North Carolina Agricultural Chemicals Manual and various crop production guides. Do not use an herbicide on a plant that is not listed on the label. If greater than 80% of the soil surface is shaded, weeds seldom become a problem. Mulch helps smother weeds that germinate in the spring (, In early spring before seeds germinate, a, Waiting for a flush of weeds to germinate and then controlling them with minimal soil disturbance can be an effective way to suppress weed populations. Hand-pulling weeds is the safest option for surrounding plants, but you need to be sure to get the entire root of the weed. It is softly hairy and the seeds are 1/16 of an inch. Perennial and biennial weeds are generally more difficult to control because they have vegetative structures that are persistent and more resilient, making these species resistant to mechanical and chemical measures. Pine Bluff, Arkansas: University Of Arkansas Division of Agriculture Cooperative Extension Service, 1981. However, by integrating cultural, mechanical, biological, and chemical methods into a weed management system, the goal of growing a relatively weed-free, aesthetically pleasing landscape or productive garden may be realized. Seed-propagated weeds can be managed by preventing germination or survival of young seedlings. Based in part on text from the 1998 Extension Master Gardener manual prepared by: Erv Evans, Extension Associate, Department of Horticultural Science, Moore, K.A., J. Neal, and L.K. A chopping hoe may be the only practical tool if the soil is rocky. No one should ever put any part of a plant in his or her mouth unless the plant has first been identified as edible. Tender, highly nutritious leaves can be sauted and eaten like spinach. Most postemergence herbicides are systemic but, as previously noted, some have only contact action. Solarization can heat the soil enough to control some disease organisms. Weeds have seeds that stay viable for a long time. Identification: Weed Photo Gallery, All Categories. In turfgrasses and ornamentals, preemergence herbicides are applied in late summer to early fall to control winter annuals such as annual bluegrass, henbit, and common chickweed. The possibility of root uptake of soil-applied herbicides depends on the herbicide, the type of soil, and its moisture content. Foliage is toxic to livestock, especially sheep, when consumed in quantity. Crabgrass, for example, was among the first grains cultivated in Europe during the Stone Age and was probably introduced to the United States in fodder. Both species have similar leaves, which are small and oblong with an irregular maroon to purple spot in their center. Here are some guidelines for eating weeds: Serious illness or even death can result when poisonous weeds are eaten. Moore, and. Be able to give examples of cultural weed controls. Smooth crabgrass may be distinguished from large crabgrass by the absence of hairs on the leaves and sheath. Remove and destroy seed heads to prevent these ornamental plants from becoming weeds in another part of the garden. The seed head is a single spike with 6 to 20 rounded burs which contain 2 seeds in each bur. Receive Email Notifications for New Publications. Always inspect composts and mulches that have been stockpiled outdoors; the presence of weeds, seeds, or material that has not decomposed is a sign that the compost pile has not been properly maintained. While some parts may be edible, others can be toxic. Hand-pulling weeds as they appear is an effective, but only temporary, way of controlling annual weeds. Cultural practices for the control of summer annual weeds are aimed at shading and crowding the young weed seedlings by producing a dense sod. Properly composted landscape debris are not be a source of weeds. Young shoots and tender tips of shoots raw, cooked, or dried for tea, Leaves sauted; flowers raw, cooked, or dried for tea, Young shoots less than 8 inches long and stems (Do not eat mature leaves. Check the label of each product before using. It very quickly sends up a flower stalk and goes to seed. Under close mowing, the broad, compressed purple sheaths of barnyardgrass lie flat on the ground and spread in a semicircular pattern. Some formulations are especially volatile, and the vapors or fumes can drift to susceptible plants. The kind of hoe selected affects the success rate in controlling weeds. It prefers rich moist soils, but it can establish itself in dry, sandy soil. But in North Carolina, it usually does not produce temperatures high enough to control weeds effectively. Harry Rose, Flickr After a frost, entire plants become straw-colored, but stems with burs can persist through the winter. Leaf margins vary, but usually are irregularly lobed. A threshold is the point at which action should be taken. It can be confused with lespedeza (Kummerowia striata) unless it is blooming. See also: Examples of perennial plants; Examples of biennial plants; Examples of vascular plants Seeds from weeds in a vacant lot or along a fence row or ditch bank can be blown or washed into a landscape, so mow the weeds before they go to seed. The seeds can sit in the soil for years. Other herbicides have little or no persistence in the soil (see the North Carolina Agricultural Chemicals Manual for additional information). Red sorrel can survive in very alkaline soils as well. For thickets, cut all stems to the ground with a mower or string trimmer. Complete soil testing is the key to proper liming and fertilization. Strategy 1 could be considered an organic approach if an organic fertilizer is used. In contrast to preemergence herbicides, the majority of postemergence herbicides do not provide residual control; that is, they control emerged weeds only and do not prevent weeds from emerging afterwards. Some factors affecting chemical management include the following: Herbicide injury to plants can often be traced to application of the wrong herbicide for the site, improper application, or application under less than optimum conditions. Lambsquarter spreads by black seeds that germinate in the late spring to early summer. ), Young leaves (must be cooked thoroughly or dried for tea) and seeds, Black medic, chamberbitter, lespedeza, prostrate knotweed, spurge, Cocklebur, lambsquarters, pigweed, prostrate knotweed, prostrate spurge, purslane, ragweed, Carpetweed, chamberbitter, mulberry weed, sida, spurge, Virginia copperleaf, Crabgrass, goosegrass, Japanese stiltgrass, Asiatic hawksbeard, bittercress, chickweed, henbit, horseweed, lawn burweed, speedwell, vetch, Asiatic hawksbeard, bittercress, Carolina geranium, chickweed, common groundsel, henbit, horseweed, shepherd's purse, sowthistle, speedwell, vetch, Aster, curly dock, dandelion, dogfennel, plantain, Virginia buttonweed, wild violet, Dandelion, dogfennel, pokeweed, Virginia buttonweed, wild violet, English ivy, Japanese honeysuckle, poison ivy, smilax, wisteria, Broomsedge, Carolina geranium, red sorrel, Appear pale and stunted: chickweed, dandelion, redroot pigweed, wild mustard, Acceptable to most weeds, including jimsonweed and morning glory, Appear lush and green: chickweed, dandelion, redroot pigweed, wild mustard, Annual bluegrass, annual lespedeza, annual sedge, broadleaf plantain, corn speedwell, goosegrass, prostrate knotweed, prostrate spurge, Alligatorweed, annual bluegrass, liverwort, moneywort, moss, pearlwort, rushes, sedges, Annual lespedeza, birdsfoot trefoil, black medic, goosegrass, bracted plantain, prostrate knotweed, spotted spurge, yellow woodsorrel, Biennial and perennial weeds, such as aster, brambles, chicory, dogfennel, goldenrod, thistle, and wild carrot, Annual bluegrass, chickweed, crabgrass, goosegrass, Winter annual weeds, such as henbit, horseweed, and pepperweed, Reduced plant growth and vigor while producing no other acute symptoms, Causes include low doses of herbicides sprayed over the top of plants when new growth is present, poor drainage, root-feeding insects, competition from weeds, low fertility, and water stress; look for untreated plants growing in similar conditions and carefully evaluate all potential causes, Feathering of leaves; strap-shaped leaves, Leaf malformations are induced by translocated herbicides, Fiddlenecking in young growing points of plants; upward curling of older leaves, Symptoms are produced by growth-hormone herbicides, Distinct cupping (usually upward) is caused by growth-hormone herbicides; also may be caused by root uptake of ALS-inhibitor herbicides, Crinkling of leaves; in grass species such as corn, leaves fail to emerge normally from the sheath and the plant remains in a stunted condition with twisted and crinkled leaves, Injury symptom on grasses can be caused by an herbicide but is more commonly caused by leaf-rolling arthropod pests, Tip chlorosis (yellowing in the actively growing regions of plants); chlorotic areas may appear yellow, white, or pinkish, Veinal chlorosis (yellowing of leaf veins), Usually results from root uptake of herbicides, lnterveinal chlorosis (yellowing of tissues between leaf veins), Typically is caused by root uptake of herbicides but is also caused by some nutrient disorders, such as Fe deficiency, Marginal chlorosis (a narrow, yellow band almost entirely around the leaf margin; sometimes called a "halo effect"), Can be caused by root or foliar uptake of herbicides, Rarely associated with herbicide injury; sometimes preemergence herbicides applied over very young plant tissues can cause puckering and mottled leaves in susceptible species such as hydrangea, heuchera, and Euonymus alatus compacta; may also be injury from foliar nematodes, White tissue; results from loss of all pigments (cartenoids and chlorophyll); tissues may be white or yellowish-white, often with pink on the leaf margins, Several herbicides labeled for use in turf may cause these symptons; some bacterial infections may mimic these symptoms, >An overdose of a herbicide can cause these symptoms, Necrosis occurring in small spots scattered through the leaf, Response often occurs within a few hours after exposure to growth-hormone herbicides, Stem elongation of broadleaved plants may be enhanced (at low concentration) or inhibited (at high concentrations) by growth-hormone herbicides, Stem cracking; stems become brittle and may break off in heavy winds; stems often crack near the soil line, Symptoms are typical of injury from growth-regulator herbicides, Can be caused by growth-hormone herbicides, Caused by growth-hormone herbicides; also a common result of stem girdling at the soil line (resulting in stem swelling above the soil line), Changes in size, shape, or arrangement of various flower parts; branched flowers; multiple spikelets; some spikelets missing; flower partly or completely enclosed in the leaf; opposite instead of alternating spikelets along the rachis (axis of an, Usually caused by growth-hormone herbicides; delay in flowering due to herbicide injury is common, Changes in size, shape, and appearance of fruit or abortion of fruit, Often associated with growth-regulator-type herbicides, spray drift or misapplication of contact-type herbicides, Development of primary and/or lateral roots is inhibited; thickened and shortened roots; usually leads to stunting of plants, Some herbicides are effective inhibitors of root growth; growth-hormone herbicides may cause swelling of roots in some plants.

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examples of biennial weeds

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