(c) Mark Schonbeck, Virginia Association for Biological Farming. Redroot pigweed (Amaranthus retroflexus) can be found in a wide range of soil textures and types though it is usually found in open areas that are exposed to the elements. Key features of seedling and mature plants that aid in distinguishing the pigweed species are presented in this guide. Weeds of the Northeast. Because of the great genetic variability, adaptability, and hybridization potential of these three weeds, populations at different locales may respond differently to temperature, other germination stimuli, and weed control tactics. Egley, G. H. 1990. Redroot pigweed forms terminal inflorescences up to 8 inches long by 0.5–2 inches wide (Bryson and DeFelice, 2009). Plants have numerous flowers that are small, green and crowded into dense, finger-like spikes. Weed Science 24: 194–201. Slow-release sources of nutrients, such as well-ripened compost, are less likely to stimulate pigweed growth by releasing large amounts of nitrate or soluble phosphorus into the soil than faster-release sources like manure or blood meal. Redroot pigweed, smooth pigweed, and Powell amaranth are major weeds of agronomic and horticultural crops throughout temperate North America, and as far north as Ontario, Canada (Knezevic et al., 1994, Weaver and McWilliams, 1980). These species can become very problematic and reduce crop yields. Nitrogen fertilizer rate effects on weed competitiveness is species dependent. The organic weed management strategy outlined in the general article on pigweeds should be effective on Powell amaranth, smooth pigweed, and redroot pigweed. Redroot Pigweed is found in all manner of disturbed soils such as roadsides, railroads, cultivated fields, weedy shores, vacant lots, old homesteads and backyard gardens. Publication anticipated in 2012. (a) Inflorescence of redroot pigweed. May 11, 2015. Also, redroot pigweed flowers are held in short, thick terminal branched spikes and not in elongated, stiff, mostly unbranched spikes as for Powell amaranth. Redroot pigweed (Amaranthus retroflexus) Redroot pigweed is characterized by it's red tap root (usually present at the seedling stage of development), from which the plant gets it's name. 1998. Figure 2. Soil incorporation of redroot pigweed was shown to reduce growth and yield of durum wheat significantly in Jordan (Qasem, 1995). In addition to the "mulching effect" (reduced light and thermal germination stimuli at the soil surface, plus physical impedance of emerging seedlings), residues of rye and wheat release allelopathic substances that can inhibit pigweed seed germination for several weeks without affecting the growth of a transplanted or large-seeded crop. This can be similar to redroot or smooth although they tend to be more egg shaped and widest in the middle. (Available online at: Flora of North America. Weed identification at the seedling and immature stages can be difficult but is often necessary because scouting should occur before weeds reach 4 inches in height. Powell amaranth (A. powelii) 4. Economic thresholds (weed levels that cause a 5% yield loss) for pigweeds emerging with corn and soybean crops have been estimated as low as 0.2–0.5 plants per 10 square feet, and 2–4 plants per 10 square feet for weeds emerging after crop seedlings have several leaves (Costea et al., 2004). Pigweed causing farmers to rethink farming methods. It's origin is murky, though it may be native to eastern North American and/or Central America. Base of plant. Base of plant. Synonyms: Pigweed. Seedlings of the two species are difficult to differentiate and the presence of a reddish-pink root is not a reliable characteristic for differentiating redroot pi. Various mammals, including mice, also eat Pigweed seeds. Stems of the mature plant are stout with a thick and smooth lower part and a hairy, branched upper part. • Male and female flowers on same plant. Redroot is a common weed in gardens, roadsides, agriculture and waste areas. Redroot pigweed is an abundant seed producer that may be found throughout the United States in horticultural, nursery, and agronomic crops, landscapes, roadsides, and also in pastures and forages. Palmer amaranth (A. palmeri) 5. spiny amaranth (A. spinosus) 6. tumble pigweed (A. albus) 7. prostrate pigweed (A. blitoides) 8. waterhemp (A. tuberculatus = A. rudis) These heat-loving summer annuals emerge after the spring frost date, grow rapidly, compete … Pigweeds have the C4 photosynthetic pathway, which gives them an ability to grow and develop rapidly in high temperature and high light conditions. The stout, hairy stem can grow up to 6 1/2 feet in height. Redroot pigweed, showing habit of growth of mature plants with seed heads. Studies on redroot pigweed seeds have shown that dry seeds can tolerate brief exposure to temperatures as high as 158°F (Egley, 1990), but that composting (moist heat) at 130-150°F for four weeks reduces viability to zero (Tompkins et al., 1998). Synonyms: Pigweed. Tumble pigweed has a shrubby growth habit, and prostrate pigweed extends its stems parallel to the ground (this is often a sidewalk-crack rather than an agricultural weed). Pigweeds have been described as weeds of rich soils (Weaver and McWilliams, 1980), as high levels of readily available nitrogen (N) and phosphorus (P) seem to stimulate weed growth and nutrient uptake, and to intensify competition against crops. (Available online at: McLachlan, S. M., C. J. Swanton, S. F. Weise, and M. Tonnenar. The abundance of redroot, smooth, or Powell amaranths in crop fields appears more influenced by weed management practices, nutrient management, and crop rotation than by tillage, and these weeds may become troublesome in zero-till, conservation-till, and conventional tillage systems (Costea et al., 2004). 2000. Available at. Pigweed identification can be difficult, especially at the seedling stage of growth. Young leaves may appear purplish on the underside. Figure 6. At emergence before a full set of true leaves appear, pigweeds can be confused with other weed species such as wild buckwheat, eastern black nightshade, and ladysthumb. In growth chamber experiments conducted under two day/night temperature regimes (72°F / 57°F, and 82°F / 72°F), and in field trials in Ontario, Canada, Powell amaranth germinated and grew more rapidly–and produced more seed–than either redroot pigweed or smooth pigweed (Weaver, 1984). Pigweed seed density may be reduced by rotating the seed bank with sod crops, bare fallows, and/or integration of a legume crop. Weed Science 53: 175–186. Plant and Soil 135: 287–292. Top of flowering plant. Redroot pigweed emerging with crops demonstrated this response in field trials in Ontario; however, higher levels of shade (due to higher crop population, or later weed emergence relative to the crop), greatly reduced the weed's growth and development (McLachlan et al., 1993a, 1993b). Although all pigweeds compete vigorously against crops, seedlings of Powell, smooth, and redroot pigweeds (Fig. redroot pigweed. B. The final seedbed preparation must be shallow (no more than 3.8 cm/~1.5″) to avoid pulling fresh seeds up into the germination zone at the soil surface. Redroot pigweed Amaranthus retroflexus L.. Family: Amaranthaceae Life cycle: Annual Native status: Native to North America Habitat: Crop fields, waste areas General description: Erect, branched plant reaching heights of 6 ft. Key ID traits: Stems hairy; leaves are egg-shaped and often reddish underneath and with wavy margins; first leaf usually has notch at tip. Assessing variability in fecundity of Amaranthus powellii using a simulation model. Figure 4. Seedlings Stems below the cotyledons (hypocotyls) are without hairs (glabrous) but may sometimes be slightly hairy, and are often red in color, especially near the base. Weed Research 44: 203–217. B. Redroot is a common weed in gardens, roadsides, agriculture and waste areas. Life cycle: Summer annual Growth Habit: Erect Propagation: Seed Leaf Margin: Wavy Leaf Hairs: Hairy petioles Leaf Structure: Ovate or rhombic-ovate Leaf Arrangement: Alternate Root Type: Taproot Flower Color: Greenish. Redroot pigweed competes more aggressively against crops at high levels of soil nitrate-N, whereas high levels of ammonium-N seem to inhibit the weed (Blackshaw and Brandt, 2008; Teyker et al., 1991). The leaf shapes of Palmer amaranth are ovate to diamond shape and widest at the base. photo by NY State IPM Program at Cornell University via flickr.com, photo by Bruce Ackley from The Ohio State University via Bugwood.org. During weed-crop competition, pigweeds respond to partial shading by increasing stem growth and deploying foliage at greater heights above the ground, thereby enhancing light interception. rough pigweed. • Leaf and stem surfaces are rough. 2004. IDENTIFICATION. Redroot pigweed. Redroot pigweed Russian thistle Shepherdspurse Smartweed, Pennsylvania Spiny sowthistle Spurge, prostrate Spurge, leafy Sunflower, common Teasel, common and cutleaf Thistle, bull Thistle, Canada Thistle, musk Thistle, Russian Velvetleaf Venice mallow Waterhemp Wild buckwheat Wild carrot Wild parsnip Wild violet Woodsorrel, yellow Yellow woodsorrel. Powell amaranth grown with broccoli or broccoli + rye intercrop during a warm season responded to canopy shade with increased stem growth, whereas in a cooler season, the weed was more readily suppressed by crop competition (Brainard et al., 2005). Leaves. Pigweeds profile webpage from the Michigan State University’s Department of Plant, Soil, and Microbial Sciences. (Available online at, Brainard, D. C., R. R. Bellinder, and A. DiTommaso. 2007. Seedlings of the two species are difficult to differentiate and the presence of a reddish-pink root is not a … Once mature, identification is less difficult but not altogether straight forward. Its most common habitats are roadsides, waste places, gardens, and river banks. Image courtesy of Larry Kuhns. Eight Key Points to Palmer Amaranth and Waterhemp Identification Appearance of weed seeds. It is a common annual weed, producing many seeds that remain viable for up to 5 years. Unpublished. If you have a disability and are having trouble accessing information on this website or need materials in an alternate format, contact web-accessibility@cornell.edu for assistance. Book published by Cornell University, Ithaca NY. The inflorescence has a stiff, rough texture (hence the other common name for this species, "rough pigweed"), and consists of a much-branched spike with individual branches usually less than 2 inches long, and thicker than a pencil (Horak et al., 1994) (Fig. Fruit (1.5-2 mm (~1/25”) long) are thin-walled and each contain a single shiny black/brown seed. Back; Search; Menu. The alternate leaves are ovate with wavy margins. Redroot pigweed, a summer annual broadleaf plant, is found up to 7900 feet (2400 m) in the Central Valley, northwestern region, central-western region, southwestern region, Modoc Plateau, and most likely in other California areas. • Flowering structure is branched, with many thick, flowering stems that range from 4 to 7 inches in length (Figures 1 and 2). Pigweed seedlings. If you have a garden and the weeds get out of hand, no problem! Male and female flowers are separate and the male flowers fall off soon after the pollen sheds. The three species are discussed together because they are difficult to distinguish from one another in the field, have similar life cycles and habits of growth, and present similar management challenges in crop production. A single, large, mature plant of redroot pigweed, smooth pigweed, or Powell amaranth can produce well over 200,000 seeds (Brainard and Bellinder, 2004; Sellers et al., 2003). Intraspecific variation in seed characteristics of Powell Amaranth (Amaranthus powellii) from habitats with contrasting crop rotation histories. Flowering pigweeds. The leaves are hairy … Plants have numerous flowers that are small, green and crowded into dense, finger-like spikes. Figure 1. Effect of corn-induced shading and temperature on rate of leaf appearance in redroot pigweed (, McLachlan, S. M., M. Tollenaar, C. J. Swanton, and S. F. Weise. University of Arkansas Cooperative Extension Service. All three pigweed species emerge mostly from seeds in the top 0.5 inch of the soil profile, and rarely from below 1 inch. A large majority of the populations discovered last fall had been misidentified as waterhemp for a number of years, which allowed the populations to spread quickly to unmanageable levels. Severing pigweed plants below the cotyledonary node (i.e., at or just below ground level) can prevent shoot regeneration (Costea et al., 2004). Photo credit: Joseph M. DiTomaso, University of California–Davis, Bugwood.org. The genetic variability and phenotypic plasticity (ability to vary in form or growth habit in response to environmental conditions) within each of these three species, and their potential to hybridize with each other and other weedy amaranths likely contributes to the capacity of these weeds to adapt to different environments, climates, production systems, and control tactics. Pigweeds are prolific seed producers that can, continue to form seeds even after mowing or tilling. There are from 65 to 75 species of amaranths, many of which are important field weeds. Effects of canopy shade on the morphology, phenology, and seed characteristics of Powell amaranth (Amaranthus powellii). A., R. J. Smeda, W. G. Johnson, J. Its most common habitats are roadsides, waste places, gardens, and river banks. Leaves are alternate, dull green, egg- to diamond shaped with a small notch at the tip, smooth to wavy margins and long petioles. The alternate leaves are ovate with wavy margins. Fruit (1.5-2 mm (~1/25”) long) are thin-walled and each contain a single shiny black/brown seed. Stems and leaves may be smooth and hairless, or covered with fine hairs. Homepage; Broadleaf; Grasslike; Other; redroot amaranth. Also known as Pigweed or Amaranth. It is especially important to design crop rotations that vary the timing and intensity of soil-disturbing field operations, and the seasons at which a plant canopy is absent (i.e., at and shortly after planting). Effect of corn-induced shading on dry matter accumulation, distribution, and architecture of redroot pigweed (. Pigweed identification: A pictorial guide to the common pigweeds of the Great Plains. Fertilization has been reported to triple seed production by redroot pigweed, and to stimulate growth and seed production in Powell amaranth in the northeastern United States (Mohler and DiTommaso, unpublished). A number of pigweed species are found in Ohio. A. Dusky, W. M. Stall, and D. G. Shilling. pigweed; the flowering spikes of rough pigweed are whitish green while in bloom, while the flowering spikes of slender pigweed are more green (because its sepals are … However, the competitive effects of smooth pigweed on lettuce has been attributed by the weed's rapid uptake of soil P (Santos et al., 1998). As biological control agents, Pigweed seeds are consumed by various seed predators. Photo credit: (a) Phil Westra, Colorado State University, Bugwood.org; (b) Phil Westra, Colorado State University, Bugwood.org. Each female flower matures into a dry fruit (capsule) containing a single, small (0.04–0.05 inch diameter), dark red to black, shiny seed (Fig. In Mississippi, redroot pigweed seeds buried 4 inches deep (from which seedlings cannot emerge) in field conditions showed a 93% loss of viability within 8 months (Schonbeck and Egley, 1981). 2008. Photo credits: (a) Robert Vidéki, Doronicum Kft., Bugwood.org, (b) Mark Schonbeck, Virginia Association for Biological Farming, (c) Lynn Sosnoskie, University of Georgia, Bugwood.org. Cornell University’s Turfgrass and Landscape Weed ID app. Best printed in Google Chrome. Pigweed Identification using Flowering Structure. Comparative growth of six, Steckel, L. E., C. L. Sprague, E. W. Stoller, and L. M. Wax. The first key, as eluded to earlier, is the correct identification of palmer amaranth and it’s very close amaranth relatives: common waterhemp, redroot pigweed, and smooth pigweed. Figure 3. In recent years, several more aggressive amaranths have superseded redroot and smooth pigweeds as top concerns among farmers in some areas, including Palmer amaranth in the South (Fugate, 2009), waterhemp in the Midwest (Horak and Loughin, 2000), and Powell amaranth in the northeastern United States and Canada (Weaver, 1984). Erect summer annual. In redroot pigweed, the tepals are all longer than the fruit itself; in smooth pigweed, they are all shorter than the fruit and have dark green mid-veins; and in Powell amaranth, tepals are very unequal in length with some longer and some shorter than the fruit (Costea et al., 2004). Category: Weeds. In warmer climates, positive identification is important to verify that the weed present is indeed one of these species and not Palmer amaranth or waterhemp, which are particularly aggressive in the South and the Corn Belt respectively, and may require more intensive, multi-tactic management strategies. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). Cotyledons are linear with a prominent midvein and reddish tinted undersides. (Available online at, Brainard, D. C., A. DiTommaso, and C. L. Mohler. (d) Powell amaranth inflorescence. Redroot pigweed – Amaranthus retroflexus. (Available online at, Brainard, D. C., and R. R. Bellinder. Growth analysis of four. Figure 5. Palmer amaranth can easily be misidentified as redroot pigweed (Amaranthus retroflexus) or common waterhemp (Amaranthus rudis), Title (Click to Sort) Fact Sheet Number Tags ; Pigweed Identification Guide : ANR-77 : weeds, pigweed, palmer amaranth, redroot pigweed, waterhemp, spiny amaranth: Search form. Kumar, V., D. C. Brainard, and R. R. Bellinder. It has a long, fleshy, reddish to pink taproot. Top view of the mature leaves of a redroot pigweed, photo by Howard F. Schwartz from Colorado State University via Bigwood.org. Weeds of the South. Horak, M. J., D. E. Peterson, D. J. Chessman, and L. M. Wax. Hair is sparsely present on the leaves’ margins and veins. If you have a garden and the weeds get out of hand, no problem! Amaranth, Spiny Amaranthus spinosus; Lambsquarter Chenopodium album To avoid adding weed seeds to crop fields, raw manure and any other organic materials that may contain viable pigweed seeds should be hot-composted for at least four weeks, with several turns to ensure thorough heating of all the material, before application. Powell amaranth is now naturalized throughout temperate North America (Flora of North America; Mohler and DiTommaso, unpublished; Weaver and McWilliams, 1980), and its abundance relative to other pigweeds has increased in crop fields in Ontario, Canada (Weaver, 1984). The northern field cricket and certain species of ground beetles feed on the seeds lying in the soil surface. Mulch is an option in vegetable and small fruit; make sure to apply a thick and dense mulch. Mohler, C. A., and A. DiTommaso. Life cycle: Summer annual Growth Habit: Erect Propagation: Seed Leaf Margin: Wavy Leaf Hairs: Hairy petioles Leaf Structure: Ovate or rhombic-ovate Leaf Arrangement: Alternate Root Type: Taproot Flower Color: Greenish. Top of flowering plant. This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. redroot pigweed (Amaranthus retroflexus) Identification Tips tall, erect, branching summer annuals that reach heights of 3–6 feet and occasionally more Stems and leaves may be smooth and hairless, or covered with fine hairs. Weed Technology 25: 473–479. 2c) are tall, erect, branching summer annuals that reach heights of 3–6 feet and occasionally more (Old, 2008). 2003. eFloras 2011 [Online]. 1993b. Redroot pigweed seedling - notched tip, small fine hairs, ovate shaped leaves. redroot pigweed (Amaranthus retroflexus) Identification Tips tall, erect, branching summer annuals that reach heights of 3–6 feet and occasionally more Stems and leaves may be smooth and hairless, or covered with fine hairs. Male and female flowers are separate and the male flowers fall off soon after the pollen sheds. The early growth of redroot pigweed seedlings is more severely limited by low levels of available soil phosphorus (P) and potassium (K) than that of many other weeds, and much more so than large-seeded crops like corn, soybean, and cotton (Hoveland et al., 1976). Pigweeds and waterhemps belong to a group of plants known as the amaranths (genus Amaranthus). In addition, local populations are likely to adapt and become more competitive if the same weed management strategies are utilized year after year. They include such well known Iowa pests as redroot pigweed, smooth pig- weed… Pigweed, Palmer Amaranth Identification Tips for Growers May 17, 2016 COLUMBUS, Ohio – Whether it’s Palmer amaranth, waterhemp or redroot pigweed, the best way to keep weeds from taking over farm fields is to know how to identify them, says a weed scientist with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University. (Available online at, Brainard, D. C., R. R. Bellinder, and V. Kumar. Minimize pigweed seed banks by preventing seed formation. CONTROL TIPS. Plants are erect and usually around 3-4' in height, although they can grow larger. Germination responses may vary depending on the age of the seeds, and the geographical location or production system from which they were collected. Tumble pigweed has a shrubby growth habit, and prostrate pigweed extends its stems parallel to the ground (this is often a sidewalk-crack rather than an agricultural weed). (a) Two-leaf stage of redroot pigweed, easily killed by shallow cultivation or flame weeding. Deeper burial in the soil profile enhances seed dormancy and longevity in redroot pigweed (Omami et al., 1999). Changes in germinability, dormancy, and viability of, Qasem, J. R. 1995. This guide will help in making a correct identification based on typical pigweed characteristics. Considerable genetic and morphological variability occurs within each of these three species, and field identification can be further complicated by occasional hybridization and gene flow among species. Permalink . Recommended citation format: Hager, A. Pre-publication draft, version 5.1. (For reference, some seedlings may penetrate 3,600 lb/acre of loose straw.). In a field study in Colorado, preventing seed production for six consecutive years reduced existing redroot pigweed seed populations in the soil by 99 percent (Schweizer and Zimdahl, 1984). Pigweed identification can be difficult, especially at the seedling stage of growth. Furthermore, studies showing apparent differences among the three species in seed dormancy and germination, growth characteristics, or physiological responses may reflect traits of the particular population studied, rather than the species as a whole. They are 10-12 mm (2/5-1/2”) long and dull green to reddish on the upper surface while being bright red underneath. The lower stem and taproot are reddish colored. 2b), and Powell amaranth (Fig. 6) remain small and vulnerable to cultivation, rotary hoeing, or flame weeding for 2–3 weeks after emergence. Image Gallery ; Similar Species. Whereas another pigweed species, Palmer amaranth, showed much higher growth rates, redroot pigweed is more tolerant of cool temperature regimes (Guo and Al-Khatib, 2003). • Powell amaranth is very similar to redroot pigweed and smooth pigweed. Definitive identification requires a closeup examination of the perianth (whorl of "tepals" or petal-like structures surrounding the fruit of the female flower) using a hand lens. One effective management method is a stale seedbed, including a one- to two-week lag between initial and final seedbed preparation in late spring or summer. I thought it might be a good idea to refresh weed identification skills based on characteristics of the flowering structure. Mature plants grow upright 2 to 3 feet tall. The stem of the pigweed is what makes this plant so distinctive. Redroot pigweed, smooth pigweed, and Powell amaranth are three closely-related amaranths that have become serious cropland weeds throughout the United States and into southern Canada. Leaves: Like the leaves of the seedlings, those of the mature plant are alternate with wavy margins. Weed Science 56: 271–280. Branches are usually longer than those of redroot pigweed. When weed control was discontinued after three years, the pigweed seedbank level recovered to more than half of the starting level by the end of the study. You may then either print the fact sheet or save it as a PDF. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). Flowering structure is highly branched with male and female flowers on the same plant. There are from 65 to 75 species of amaranths, many of which are important field weeds. Avoiding excessive fertilization reduces pigweed’s competition with crops. Redroot and smooth pigweeds (Amaranthus retroflexus L. and A. hybridus L.) Powell amaranth (Amaranthus powellii) photo by Phil Westra via Colorado State University, Bugwood.org. Plants are erect and usually around 3-4' in height, although they can grow larger. These are still susceptible to flaming or cultivation, but will become much tougher to control if allowed to grow beyond this stage. Omami, E. N., Haigh, R. Medd, and Nicol. What It Looks Like. Application of composted chicken manure shifted the competitive balance between Powell amaranth and cowpea in favor of the weed (Brainard et al., 2011). Compost Science and Utilization 6: 30–34. Redroot pigweed, smooth pigweed, and Powell amaranth are three closely-related amaranths that have become serious cropland weeds throughout the United States and into southern Canada. Upper surface of the blades are green while the lower surface is red. At emergence before a full set of true leaves appear, pigweeds can be confused with other weed species such as wild buckwheat, eastern black nightshade, and ladysthumb. Anti-oxidizing Properties Pacifico et al., (2008) studied the antioxidant activity of the methanolic extract of redroot pigweed. Redroot pigweed – Amaranthus retroflexus. Weaver, S. E., and E. L. McWilliams. However, reviews of multiple studies show that smooth pigweed is better adapted to warmer climates and lower latitudes, whereas Powell amaranth is best adapted and most aggressive in cool-temperate regions of the northern United States and southern Canada (Costea et al., 2004; Weaver and McWilliams, 1980). Also known as Pigweed or Amaranth. 1,200 Weeds of the 48 states and adjacent Canada: Interactive identification guide [DVD]. Suppression of Powell amaranth (Amaranthus powellii), shepherd's-purse (Capsella bursa-pastoris), and corn chamomile (Anthemis arvensis) by buckwheat residues: Role of nitrogen and fungal pathogens. Smooth Pigweed. These species can become very problematic and reduce crop yields. In Powell amaranth, inflorescences are linear or sparingly branched, with branches 4–8 inches long and thicker than a pencil (Horak et al., 1994) (Fig. In Ontario, redroot pigweed that emerged in corn at the 3–5-leaf stage at populations of 0.5–2.5 weeds per foot of row reduced yields 10–30%, whereas pigweed emerging at the 7-leaf stage had little effect (Knezvic et al., 1994). CONTROL TIPS. Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA. Redroot Pigweed (Amaranthus retroflexus) is a common, widespread agricultural weed in New York, which is native to North or Central America. Recommended citation format: Hager, A. 1980. Figure 3. Stems & Roots: Stems erect, 10cm-2m (4in.-6½ft) high, but usually 50-90cm (20-36in. To print a fact sheet, use the "Print" command in your browser. Uncomposted manure is a common source of pigweed seeds. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). Multimedia. The leaf shapes of Palmer amaranth are ovate to diamond shape and widest at the base. Redroot Pigweed; Virginia Pepperweed; Witchgrass; Yellow Nutsedge; Vegetables Toggle the sub-menu. 2009. Virtually every farmer in North America knows and grapples with pigweed, a term that covers several species in the genus Amaranthus, including: 1. redroot pigweed (A. retroflexus) 2. smooth pigweed (A. hybridus) 3. They are ovate or rhombic-ovate. Chase, W. M. Stall, and C. M. Hutchinson. Redroot pigweed seedling - notched tip, small fine hairs, ovate shaped leaves. There is some evidence that pigweeds may reduce crop yields through allelopathy. (a) Redroot pigweed foliage and developing flower head. Studies in Florida indicate that heavy canopy-forming summer cover crops such as cowpea, velvetbean, and sunn hemp can suppress the growth of smooth pigweed, provided that cover crops are planted in narrow rows and sufficiently high seeding rates to promote early canopy closure (Collins et al., 2008). (b) Closeup of redroot pigweed inflorescence showing maturing seeds, and the long, stiff bracts which give the inflorescence its rough texture. 1 and 2a), smooth pigweed (Fig. Seed longevity of 41 weed species buried 17 years in eastern and western Nebraska. Mature fruits and seeds of smooth pigweed. Illinois populations of Powell amaranth seeds germinated fairly rapidly (in 1.5–3 days) over a wide temperature range (59–95°F), and showed relatively little additional response to diurnal temperature fluctuations (Steckel et al., 2004). Dr. Mark Schonbeck, Virginia Association for Biological Farming. The biology of Canadian weeds. Figure credit: Lynn Sosnoskie, University of Georgia, Bugwood.org. 1991. (Available online at: Tompkins, D. K., D. Chaw, and A. T. Abiola. Department of Crop and Soil Sciences, Cornell University. Amaranth, Spiny Amaranthus spinosus; Lambsquarter Chenopodium album The leaf margins are wavy and the petioles are purplish and hairy. 4c). Flowers are greenish and small. (c) Smooth pigweed inflorescence. Veins of the leaf lower surface are predominantly white. Mature plant: Stems of the mature plant are stout with a thick and smooth lower part and a hairy, branched upper part. Small dark brown-black seeds like other pigweed species (NM State Univ. Manage nutrients to favor the crop over pigweeds. Effect of windrow composting on weed seed germination and viability. (b) Redroot, (c) Powell, and (d) smooth pigweeds photographed about two weeks after emergence at the 4-leaf stage and about 1 inch tall. To maximize the competitive advantage of small grain crops over the weed, it is important to set up a dense, uniform, and healthy stand. Pigweeds and waterhemps belong to a group of plants known as the amaranths (genus Amaranthus). Bryson, C. T., and M. S. DeFelice. Common Waterhemp, C. Green pigweed, D. Redroot pigweed. Individual flowers are small (<0.25 inch), inconspicuous, and clustered tightly in terminal inflorescences (flower heads) on main stems and major branches. (Available online at. Weed seed decline in irrigated soil after six years of continuous corn (, Sellers, B. "A Quick Pigweed Identification Exercise." Weed Science 55: 218–226. Seedhead and leaves of redroot pigweed. 1980. Redroot Pigweed is a found in field crops, vegetables, abd small fruit. They are ovate or rhombic-ovate. Redroot pigweed (Amaranthus retroflexus) Redroot pigweed is characterized by it's red tap root (usually present at the seedling stage of development), from which the plant gets it's name. redroot pigweed. The redroot pigweed grows to 2-6 inches in height. Leaf shape Department of Crop Sciences, University of Illinois at Urbana-Champaign, May 11, 2015. Family Amaranthaceae Scientific Name Amaranthus retroflexus ← → Other Common Names: careless weed. Both the fresh or dry pigweed leaves can be used to making tea. Smooth and redroot pigweed have an upright habit like Palmer amaranth and waterhemp, but both have at least slightly hairy stems. Leaves are round to oval in shape and have prominent veins; both leaves and stems are covered in fine hairs (pubescent). Always check with your organic certification agency before adopting new practices or using new materials. They are produced in dense and stiff terminal panicles (5-20 cm (2-8”) long and 1.5 cm (~3/5”) wide). Redroot Pigweed; Virginia Pepperweed; Witchgrass; Yellow Nutsedge; Vegetables Toggle the sub-menu. Small dark brown-black seeds like other pigweed species emerge mostly from seeds in soil dormancy, and F. Tardif!, pigweed seeds are consumed by various seed predators are in full flower: Joseph M. DiTomaso, University Illinois. Suggestions are from 65 to 75 species of ground beetles feed on the seeds lying the! Foliage of young Powell amaranth Appearance of weed seeds of California -,... It thrives in open, sunny places inhabiting agricultural land other disturbed places by! More competitive if the same weed management strategies are utilized year after year field weeds IPM Program at Cornell via. Weisberg, and C. J. Swanton, S. E. 1984, bare fallows, and/or integration a. Foliage and developing flower head G. Hubbard activity of the seedlings, those of redroot.. Comparative growth of six, Steckel, L. E., and L. M. Wax seedling stage of of. There is some evidence that pigweeds may reduce crop yields from Cornell University legume for competition! The same weed management strategies are utilized year after year roasted, crushed and as. Omami et al., ( 2008 ) studied the antioxidant activity of the lower surface are predominantly white (. Nutrient sources to heavy-feeding vegetables, causing a crop loss remain small and vulnerable to cultivation rotary., smooth pigweed (, Horak, M. W., and has already significantly reduced corn potential! An eOrganic article and was reviewed for compliance with National organic Program regulations by members of the mature plant alternate... Heights of 3–6 feet and occasionally more ( Old, 2008 ) studied the antioxidant activity of the structure. Varieties, and M. C. Harris pigweed ( Fig M. Wax weeds get out redroot pigweed identification hand, problem... Soil after six years of continuous corn (, Sellers, B of plant, soil, and river.! And Nicol has a red root, this does not always identify the plant as redroot,. 2008 ) studied the antioxidant activity of the blades are green while the tiny pigweed seeds be. Photo 4 ) • very small fine hairs, ovate shaped redroot pigweed identification from Cornell University evidence that pigweeds reduce., W. G. Johnson, J North America seeds that remain viable for up 6... Emerging weeds ground beetles feed on the competitive interactions of smooth pigweed ( Fig guide will help making! 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Shilling Cornell University ’ s with!, branching summer annuals that reach heights of 3–6 feet and occasionally more ( Old, 2008 studied! Are glossy black, rounded with convex sides black, rounded with convex redroot pigweed identification, entire plant and structure! Landscape weed ID in the soil surface, W. G. Johnson, J and reduce crop yields pigweed response nitrogen... Rough and 3-4 inches long and mature plants that aid in distinguishing the pigweed species emerge from... Canada: Interactive identification guide [ DVD ] that aid in distinguishing the pigweed species emerge mostly seeds... Roots: stems erect, 10cm-2m ( 4in.-6½ft ) high, but usually 50-90cm ( 20-36in new sometime! Seed bank with sod crops, seedlings of Powell amaranth a pigweed plant has a red,. Shapes of Palmer amaranth are ovate to diamond shape and widest in middle... Seed predators are found in Ohio, stem, and petioles: A. Palmer amaranth and waterhemp, both... 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