Pigweed identification can be difficult, especially at the seedling stage of growth. 2b), and Powell amaranth (Fig. (c) Joseph M. DiTomaso, University of California-Davis, Bugwood.org, (d) Mark Schonbeck, Virginia Association for Biological Farming. Homepage; Broadleaf; Grasslike; Other; redroot amaranth. Weed seed decline in irrigated soil after six years of continuous corn (, Sellers, B. These species can become very problematic and reduce crop yields. Stems have rough surfaces and can reach up to 2 m (6.5 ft) in height but are usually smaller. 4a and 4b). Suppression of Powell amaranth (Amaranthus powellii) by buckwheat residues: Role of allelopathy. A buckwheat green manure suppressed the emergence and growth of Powell amaranth, partly by taking up available soil N, and partly by releasing allelopathic compounds from decaying buckwheat residues (Kumar et al., 2008, 2009). Guo, P., and K. Al-Khatib. 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. Presence of hairs on the leaves, stem, and petioles indicates that it is redroot or smooth pigweed. 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. May 11, 2015. 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. Figure 3. 2005. Old, R. 2008. Green and smooth pigweed very similar. 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). • Male and female flowers on same plant. Although seed longevity in soil up to 20 years has been reported, the majority of seeds either germinate or become nonviable within several years after they are shed. Identifying the Enemy; September 7, 2001: Accurate identification of Amaranthus (pigweed) species can be very difficult, especially during early vegetative development because many of these species exhibit similar morphological characteristics (i.e., many look very similar). Plants are erect and usually around 3-4' in height, although they can grow larger. Welcome to the public website of eOrganic, the Organic Agriculture Community of eXtension, Funding for eOrganic is provided by USDA NIFA and other grant programs including Western SARE, Joseph M. DiTomaso, University of California–Davis, Bugwood.org, Phil Westra, Colorado State University, Bugwood.org, http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3180.2004.00392.x/abstract, http://dx.doi.org/10.1614/WT-D-10-00134.1, http://pubs.aic.ca/doi/abs/10.4141/P02-183#citart1, http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200006982, http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242415662, http://dx.doi.org/10.1614/0043-1745(2000)048[0347:GAOFAS]2.0.CO%3B2, http://www.ksre.ksu.edu/bookstore/Item.aspx?catId=236&pubId=1754, http://dx.doi.org/10.1046/j.1365-3180.1999.00149.x, http://dx.doi.org/10.1111/j.1365-3180.1995.tb02015.x, http://dx.doi.org/10.1111/1365-3040.ep11611005, http://dx.doi.org/10.1614/0043-1745(2003)051[0329%3ACGOSAS]2.0.CO%3B2, https://doi.org/10.1080/1065657X.1998.10701906, Blackshaw, R. E., and R. N. Brandt. Palmer amaranth (Amaranthus palmeri) … 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. 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 … A Quick Pigweed Identification Exercise Aaron Hager. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). These species can become very problematic and reduce crop yields. Interference of redroot pigweed (Amaranthus retroflexus), Palmer amaranth (A. palmeri), and common waterhemp (A. rudis) in soybean - Volume 51 Issue 1 - … Redroot pigweed (Figs. Permalink . Flowers/Fruits: Flowers are greenish and small. 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. Male and female flowers are borne together on the same plant (monoecious). A. 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. Because redroot pigweed can hybridize with other amaranth species, identification to species … • Leaf and stem surfaces are rough. The stems are erect, light green, stout, branched, 60 … Pigweed seedlings. 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. This guide will help in making a correct identification based on typical pigweed characteristics. rough pigweed. (a) Redroot pigweed foliage and developing flower head. 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 … 1998. Pigweed seed density may be reduced by rotating the seed bank with sod crops, bare fallows, and/or integration of a legume crop. The biology of Canadian weeds. Weed Science 56:743–747. 6) remain small and vulnerable to cultivation, rotary hoeing, or flame weeding for 2–3 weeks after emergence. 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). 1994. The leaf margins are wavy and the petioles are purplish and hairy. Plants are erect and usually around 3-4' in height, although they can grow larger. (a) Two-leaf stage of redroot pigweed, easily killed by shallow cultivation or flame weeding. Redroot pigweed. 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). XID Services, Inc., Pullman, WA. Stems of the mature plant are stout with a thick and smooth lower part and a hairy, branched upper part. 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. Once mature, identification is less difficult but not altogether straight forward. For more information, refer to eOrganic's articles on organic certification. "A Quick Pigweed Identification Exercise." Figure 1. The redroot pigweed emerged shortly after the corn, and has already significantly reduced corn yield potential. High-temperature effects on germination and survival of weed seeds in soil. 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. 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. Mature plant: Stems of the mature plant are stout with a thick and smooth lower part and a hairy, branched upper part. 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. Recommended citation format: Hager, A. redroot pigweed. CONTROL TIPS. Redroot pigweed (Figs. (b) Closeup of redroot pigweed inflorescence showing maturing seeds, and the long, stiff bracts which give the inflorescence its rough texture. (Available online at: Kumar, V., D. C. Brainard, and R. R. Bellinder. Amaranth, Spiny Amaranthus spinosus; Lambsquarter Chenopodium album 2011. 2003. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). Summer cover crops and green manures provide a competitive canopy during the season of greatest emergence and growth of these three pigweeds. Male and female flowers are separate and the male flowers fall off soon after the pollen sheds. Redroot Pigweed (Amaranthus retroflexus) is a common, widespread agricultural weed in New York, which is native to North or Central America. Dr. Mark Schonbeck, Virginia Association for Biological Farming. 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. Omami, E. N., Haigh, R. Medd, and Nicol. 2008. Cooperative Extension Service, Kansas State University. The biology of Canadian weeds. (Available online at, Brainard, D. C., R. R. Bellinder, and V. Kumar. Pigweed identification can be difficult, especially in the early stages of seedling growth as many species look the same. Leaves. The leaf blades taper to rounded or… May 11, 2015. 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. To maximize the competitive advantage of small grain crops over the weed, it is important to set up a dense, uniform, and healthy stand. (Available online at: Tompkins, D. K., D. Chaw, and A. T. Abiola. Top of flowering plant. Plant and Soil 135: 287–292. Veins of the leaf lower surface are predominantly white. Redroot and smooth pigweeds have spread throughout temperate regions around the world, and their long-standing reputation as troublesome summer annual weeds has led to an extensive body of research on their seed dormancy and germination, plant growth characteristics, competition with crops, and response to control tactics. 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. The stems are erect, light green, stout, branched, 60 … Flowering structure is highly branched with male and female flowers on the same plant. Weed Identification. These are still susceptible to flaming or cultivation, but will become much tougher to control if allowed to grow beyond this stage. 1 and 2a), smooth pigweed (Fig. Blades are dull and green above while hairy beneath or at least along the veins. They are produced in dense and stiff terminal panicles (5-20 cm (2-8”) long and 1.5 cm (~3/5”) wide). MATURE (photo 4) • Very small fine hairs are found throughout plant. For high value crops, it pays to manually remove any large pigweeds that have escaped early season cultivation, flame weeding, or mulching before they can form mature seed–as soon as you see flower heads start to form, if not sooner. 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. Optimum densities of three leguminous cover crops for suppression of smooth pigweed (Amaranthus hybridus). Redroot Pigweed; Virginia Pepperweed; Witchgrass; Yellow Nutsedge; Vegetables Toggle the sub-menu. 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). 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. Small dark brown-black seeds like other pigweed species (NM State Univ. Back; Search; Menu. (Available online at. It has a long, fleshy, reddish to pink taproot. Changes in germinability, dormancy, and viability of, Qasem, J. R. 1995. Weed Technology 25: 473–479. Effect of windrow composting on weed seed germination and viability. 2003. 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. Plants have a long, fleshy, reddish to pink taproot and stems that are erect, light green, branched, 23-35 inches high, rough and angular. Also known as Pigweed or Amaranth. Figure 6. Choose locally adapted cover crop varieties, and plant a combination of grass and legume for greatest competition against emerging weeds. (Available online at: Hoveland, C. S., G. A. Buchanan, and M. C. Harris. 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. (Available online at: Weaver, S. E. 1984. It particularly thrives under the sunny, fertile conditions typical of agricultural fields. Pigweeds have the C4 photosynthetic pathway, which gives them an ability to grow and develop rapidly in high temperature and high light conditions. Pigweed seed density may be reduced by rotating the seed bank with sod crops, bare fallows, and/or integration of a legume crop. 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). Redroot pigweed – Amaranthus retroflexus. Leaves. Synonyms: Pigweed. However, in Nebraska, 7% of seeds buried at a depth of 8 inches remained viable after 12 years, and 1% after 17 years (Burnside et al., 1996), and other studies have also shown greater longevity in the soil in cooler climates (Costea et al., 2004). Germination responses may vary depending on the age of the seeds, and the geographical location or production system from which they were collected. It's origin is murky, though it may be native to eastern North American and/or Central America. 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). The leaf shapes of Palmer amaranth are ovate to diamond shape and widest at the base. 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. A. Stems and leaves may be smooth and hairless, or covered with fine hairs. (Available online at: Flora of North America. 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). (Available online at: Costea, M., S. E. Weaver, and F. J. Tardif. Image Gallery ; Similar Species. 1 and 2a), smooth pigweed (Fig. Redroot pigweed has a relatively short, thick, compact inflorescence, with the uppermost central spike extending only a short distance above the first branches of the panicle. When the crop is large enough to tolerate inter-row cultivation, slightly hilling before pigweed’s first true leaves emerge will control plants in the crop row. Image courtesy of Larry Kuhns. Look for an upcoming book from Dr. Mohler on ecological management of weeds, from Cornell University Press. Redroot and smooth pigweed will have obvious fine hairs on the stems and leaf surfaces, whereas Palmer amaranth will be hairless. Mature Redroot Pigweed plant with flowers. Weed Science 53: 175–186. Common Waterhemp, C. Green pigweed, D. Redroot pigweed. Redroot Pigweed. The alternate leaves are ovate with wavy margins. In the axils of the lower leaves are small clusters of flowers arranged on a branched stem (inflorescences). Pigweed causing farmers to rethink farming methods. A Quick Pigweed Identification Exercise Aaron Hager. Amaranthus retroflexus L. Amaranthaceae (Amaranth family) Life cycle. Seeds are glossy black, rounded with convex sides. 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. Mature plants grow upright 2 to 3 feet tall. Phosphorus effects on the competitive interactions of smooth pigweed (, Schonbeck, M. W., and G. H. Egley. Stems & Roots: Stems erect, 10cm-2m (4in.-6½ft) high, but usually 50-90cm (20-36in. The distinctly red or pink taproot and lower stem for which redroot pigweed was named is not a definitive characteristic of this species, as other Amaranthus species, including smooth pigweed and Powell amaranth, sometimes show similar coloration. Male and female flowers are separate and the male flowers fall off soon after the pollen sheds. Its most common habitats are roadsides, waste places, gardens, and river banks. Photo credit: Joseph M. DiTomaso, University of California–Davis, Bugwood.org. Available at. Severing pigweed plants below the cotyledonary node (i.e., at or just below ground level) can prevent shoot regeneration (Costea et al., 2004). Redroot pigweed – Amaranthus retroflexus. Leaves are diamond-shaped to oval or egg-shaped with the broader end nearest the petiole (ovate). The leaf shapes of Palmer amaranth are ovate to diamond shape and widest at the base. Seedlings of the two species are difficult to differentiate and the presence of a reddish-pink root is not a … Individual flowers are small (<0.25 inch), inconspicuous, and clustered tightly in terminal inflorescences (flower heads) on main stems and major branches. The northern field cricket and certain species of ground beetles feed on the seeds lying in the soil surface. Pigweeds and waterhemps belong to a group of plants known as the amaranths (genus Amaranthus). (Available online at, Brainard, D. C., and R. R. Bellinder. Redroot pigweed (, Schonbeck, M. W., and G. H. Egley. Redroot pigweed. Weaver, S. E., and E. L. McWilliams. 2004. Amaranth, Spiny Amaranthus spinosus; Lambsquarter Chenopodium album Top of flowering plant. The goal is to "keep the weed guessing" by varying the timing of cultivation, crop competition, and other stresses on the weed population. Both the fresh or dry pigweed leaves can be used to making tea. (b) Smooth pigweed foliage. 5), and may overtop lower growing vegetables, causing a crop loss. Leaves are round to oval in shape and have prominent veins; both leaves and stems are covered in fine hairs (pubescent). Comparative growth of six, Steckel, L. E., C. L. Sprague, E. W. Stoller, and L. M. Wax. 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. Base of plant. 1984. This can be similar to redroot or smooth although they tend to be more egg shaped and widest in the middle. Veins of the leaf lower surface are predominantly white. Leaves. Weed Science 55: 218–226. (Available online at: McLachlan, S. M., C. J. Swanton, S. F. Weise, and M. Tonnenar. (Available online at, Brainard, D. C., A. DiTommaso, and C. L. Mohler. Redroot Pigweed. 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. In the axils of the lower leaves are small clusters of flowers arranged on a branched stem (inflorescences). (Available online at, Brainard, D. C., R. R. Bellinder, and A. DiTommaso. 1998. Interference of redroot pigweed (. Deeper burial in the soil profile enhances seed dormancy and longevity in redroot pigweed (Omami et al., 1999). 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). Seed maturation generally occurs a few weeks earlier in Powell amaranth and northern populations of redroot pigweed than in smooth pigweed; thus, the former two species are better able to complete their life cycle within a short frost-free season. 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. Bryson, C. T., and M. S. DeFelice. This erect summer annual can be found flowering from July through October. 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. (Available online at: Collins, A. S., C. A. (d) Powell amaranth inflorescence. Also known as Pigweed or Amaranth. If you have a garden and the weeds get out of hand, no problem! Redroot pigweed forms terminal inflorescences up to 8 inches long by 0.5–2 inches wide (Bryson and DeFelice, 2009). 1993a. 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. 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. Photo credit: Phil Westra, Colorado State University, Bugwood.org. Title (Click to Sort) Fact Sheet Number Tags ; Pigweed Identification Guide : ANR-77 : weeds, pigweed, palmer amaranth, redroot pigweed, waterhemp, spiny amaranth: Search form. Amaranthus retroflexus L. Amaranthaceae (Amaranth family) Life cycle. Seedhead and leaves of redroot pigweed. 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). photo by Robert Videki via Doronicum Kft., Bugwood.org, Click above for the chemical control of Redroot Pigweed from the Cornell Weed ID site. 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. Grass-legume mixtures and soil fertility affect cover crop performance and weed seed production. It thrives in open, sunny places inhabiting agricultural land other disturbed places. A number of pigweed species are found in Ohio. Also, redroot pigweed flowers are held in short, thick terminal branched spikes and not in elongated, stiff, mostly unbranched spikes as for Powell amaranth. 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). Photo credit: Mark Schonbeck, Virginia Association for Biological Farming. 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). Recommended citation format: Hager, A. Publication anticipated in 2012. Base of plant. Smaller inflorescences may also occur in upper leaf axils. 4d). 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. • Flowering structure is branched, with many thick, flowering stems that range from 4 to 7 inches in length (Figures 1 and 2). Department of Crop Sciences, University of Illinois at Urbana-Champaign, May 11, 2015. Pre-publication draft, version 5.1. 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). Pigweed (Amaranth) species leaves and petioles: A. Palmer amaranth female plant, B. 4c). This can be similar to redroot or smooth although they tend to be more egg shaped and widest in the middle. They include such well known Iowa pests as redroot pigweed, smooth pig- … Redroot Pigweed Seedling: Redroot Pigweed Flowers: Redroot pigweed is a summer annual that reproduces only by seed. The redroot pigweed grows to 2-6 inches in height. Cotyledons are linear with a prominent midvein and reddish tinted undersides. Weed Science 38: 429–435. It has a long, fleshy, reddish to pink taproot. In addition, the pigweeds: Palmer amaranth, waterhemp, redroot pigweed, Powell amaranth, and smooth pigweed, are not easily separated by species at the immature stages. Unpublished. 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. The redroot pigweed grows to 2-6 inches in height. Weed Science 56:753–761. Synonyms: Pigweed. Weed Science 57: 66–73. B. 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. Branches are usually longer than those of redroot pigweed. photo by NY State IPM Program at Cornell University via flickr.com, photo by Bruce Ackley from The Ohio State University via Bugwood.org. (c) Mark Schonbeck, Virginia Association for Biological Farming. Freshly formed seeds require higher temperatures than seeds that have overwintered in the soil (Mohler and DiTommaso, unpublished; Schonbeck and Egley, 1981). 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. The leaves are hairy on the lower surface, along the prominent veins. Effect of corn-induced shading on dry matter accumulation, distribution, and architecture of redroot pigweed (. Erect summer annual. redroot pigweed. Here are some tips to identify these four weeds from the seedling stage through plant maturity. IDENTIFICATION. The stout, hairy stem can grow up to 6 1/2 feet in height. 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). Redroot pigweed grows in cultivated fields, pastures, roadside ditches, and undeveloped areas. Redroot pigweed and smooth pigweed are native to North America and Central America, occurring as pioneer plants of riparian regions, while Powell amaranth is native to dry, mountainous regions in the southwestern United States and Mexico (Costea et al., 2004; Flora of North America). Department of Crop Sciences, University of Illinois at Urbana-Champaign, May 11, 2015. Leaves are alternate, dull green, egg- to diamond shaped with a small notch at the tip, smooth to wavy margins and long petioles. Multimedia. Redroot pigweed. Redroot Pigweed; Virginia Pepperweed; Witchgrass; Yellow Nutsedge; Vegetables Toggle the sub-menu. Manage weeds on your farm: A guide to ecological strategies. Hair is sparsely present on the leaves’ margins and veins. 1993b. • Branches of the flowering structure are compact, usually more than 11⁄2 inches long, and thinner than a pencil. 1996. Eight Key Points to Palmer Amaranth and Waterhemp Identification Appearance of weed seeds. The leaves are alternate, stalked, dull green, oval-shaped, rough and 3-4 inches long. To print a fact sheet, use the "Print" command in your browser. IDENTIFICATION. The lower stem and taproot are reddish colored. • Powell amaranth is very similar to redroot pigweed and smooth pigweed. In addition, local populations are likely to adapt and become more competitive if the same weed management strategies are utilized year after year. Stems & Roots: Stems erect, 10cm-2m (4in.-6½ft) high, but usually 50-90cm (20-36in. The leaves are alternate, stalked, dull green, oval-shaped, rough and 3-4 inches long. Plants have a long, fleshy, reddish to pink taproot and stems that are erect, light green, branched, 23-35 inches high, rough and angular. Pigweeds are prolific seed producers that cancontinue to form seeds even after mowing or tilling, so it is important to clean up fields soon after harvest and Remove plants that have flowered from the field. Egley, G. H. 1990. Permalink . The organic weed management strategy outlined in the general article on pigweeds should be effective on Powell amaranth, smooth pigweed, and redroot pigweed. Timely cultivations or flame weeding during late spring and early summer, followed by organic mulch, have been found effective for managing Powell amaranth in upstate New York (Mohler and DiTommaso, unpublished), and are likely equally effective for smooth and redroot pigweeds. Stems have rough surfaces and can reach up to 2 m (6.5 ft) in height but are usually smaller. 1981. The inflorescence of smooth pigweed is similar in size and degree of branching, but has a much softer texture (hence, "smooth pigweed"), and individual branches usually no thicker than a pencil (Horak et al., 1994) (Fig. Blades are dull and green above while hairy beneath or at least along the veins. The leaf blades taper to rounded or… Figure 5. Pigweed identification: A pictorial guide to the common pigweeds of the Great Plains. Manage nutrients to favor the crop over pigweeds. Weed Research 44: 203–217. Try to get a positive identification of the species present, and be aware that Powell amaranth may grow more rapidly in the northern United States, and smooth pigweed more so further south. Like the leaves of the seedlings, those of the mature plant are alternate with wavy margins. (b) Steve Dewey, Utah State University, Bugwood.org. Key features of seedling and mature plants that aid in distinguishing the pigweed species are presented in this guide. Seedlings: Cotyledons of the redroot pigweed plant are narrow and have a sharp end. Slender pigweed, also known as Green pigweed Cotyledons are linear with a prominent midvein and reddish tinted undersides. Application of composted chicken manure shifted the competitive balance between Powell amaranth and cowpea in favor of the weed (Brainard et al., 2011). Its most common habitats are roadsides, waste places, gardens, and river banks. 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. 2c) are tall, erect, branching summer annuals that reach heights of 3–6 feet and occasionally more (Old, 2008). Upper surface of the blades are green while the lower surface is red. Avoid broadcast applications of chicken litter or other concentrated nutrient sources, as these will stimulate rapid early growth of pigweeds, which may take up most of the nutrients before the crop can access them. Always check with your organic certification agency before adopting new practices or using new materials. Image Gallery ; Similar Species. Figure 4. Close mowing or weed-whacking between crop rows can greatly reduce seed formation, though axillary buds at basal leaf nodes on the stem can regenerate side shoots and thereby set seed. 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. Image courtesy of Larry Kuhns. 1994. 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. Figure 3. For example, seeds from Powell amaranth growing on dairy farms in upstate New York with a corn – alfalfa (multi-year) rotation were more dormant and longer lived than Powell amaranth seeds from fields under intensive vegetable production (Brainard et al., 2007). Fruit (1.5-2 mm (~1/25”) long) are thin-walled and each contain a single shiny black/brown seed. Department of Crop and Soil Sciences, Cornell University. Use in-row drip irrigation to deliver water and liquid fertilizers such as fish emulsion preferentially to the crop. 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). All three pigweed species emerge mostly from seeds in the top 0.5 inch of the soil profile, and rarely from below 1 inch. 2c) … 130. Smooth Pigweed. Redroot Pigweed is a found in field crops, vegetables, abd small fruit. When applying more concentrated nutrient sources to heavy-feeding vegetables, band the material in the crop row to avoid feeding between-row weeds. (b) Redroot, (c) Powell, and (d) smooth pigweeds photographed about two weeks after emergence at the 4-leaf stage and about 1 inch tall. Growth analysis of four. Temperature effects on germination and growth of redroot pigweed (, Horak, M. J., and T. M. Loughin. 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). Table 1. If those weeds are Redroot Pigweed Amaranth. 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). 1980. Stems are erect, and can grow anywhere from 10 cm - 2 m high, but usually 50 - 90 cm, simple or branched, lower part thick and smooth, upper part usually rough with dense short hair, greenish to slightly reddish but usually red near the roots. Powell amaranth (A. powelii) 4. 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). 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). Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA. Temperature effects on germination of nine. Mature fruits and seeds of smooth pigweed. 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. 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. Pigweeds profile webpage from the Michigan State University’s Department of Plant, Soil, and Microbial Sciences. • At maturity, entire plant and flowering structure are usually either green or reddish purple. Habit. Avoiding excessive fertilization reduces pigweed’s competition with crops. eFloras 2011 [Online]. 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. There are from 65 to 75 species of amaranths, many of which are important field weeds. 2004. If you have a garden and the weeds get out of hand, no problem! They are produced in dense and stiff terminal panicles (5-20 cm (2-8”) long and 1.5 cm (~3/5”) wide). Many cultivation implements can be adjusted to move sufficient soil into rows of established crops to bury within-row pigweed seedlings that are less than 1 inch tall. Identifying the differences between Palmer amaranth and common waterhemp (both species are hairless) is much more difficult, especially at a young age. There is some evidence that pigweeds may reduce crop yields through allelopathy. Search . 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. They are ovate or rhombic-ovate. 2009. Pigweed Identification using Flowering Structure. Figure 2. Two common weeds that are mistaken for Palmer amaranth and waterhemp are redroot pigweed and Powell amaranth. What It Looks Like. B. Redroot is a common weed in gardens, roadsides, agriculture and waste areas. Green and smooth pigweed very similar. Weeds of the Northeast. 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 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. Soil incorporation of redroot pigweed was shown to reduce growth and yield of durum wheat significantly in Jordan (Qasem, 1995). Smooth and redroot pigweed have an upright habit like Palmer amaranth and waterhemp, but both have at least slightly hairy stems. (c) Foliage of young Powell amaranth plants. They are ovate or rhombic-ovate. The alternate leaves are ovate with wavy margins. (d) Ohio State Weed Lab Archive, The Ohio State University, Bugwood.org. Fugate, L. 2009. Also, redroot pigweed flowers are held in short, thick terminal branched spikes and not in elongated, stiff, mostly unbranched spikes as for Powell amaranth. 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). Amaranth Identification The first and often critical key to managing Palmer amaranth, or any weed for that matter, is to scout and identify the species that exist in each agronomic field. Redroot is a common weed in gardens, roadsides, agriculture and waste areas. 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. Redroot pigweed grows in cultivated fields, pastures, roadside ditches, and undeveloped areas. The leaves are hairy … Minimize pigweed seed banks by preventing seed formation. 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). Chase, W. M. Stall, and C. M. Hutchinson. Pigweed identification can be difficult, especially at the seedling stage of growth. Changes in sensitivity of, Schweizer, E. E., and R. L. Zimdahl. It is a common annual weed, producing many seeds that remain viable for up to 5 years. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019. A. Dusky, W. M. Stall, and D. G. Shilling. Flowering pigweeds. Effects of canopy shade on the morphology, phenology, and seed characteristics of Powell amaranth (Amaranthus powellii). Although reducing tillage may not in itself lower pigweed populations or help in the management of these weeds, surface residues of winter cover crops rolled down for no-till planting of a subsequent production crop may be quite effective. 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. Identification of Palmer amaranth and waterhemp Proper identification is an important component of managing Palmer amaranth and waterhemp. University of Arkansas Cooperative Extension Service. photo by Phil Westra via Colorado State University, Bugwood.org. 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. 1 2 3 4 1980. Plants are erect and usually around 3-4' in height, although they can grow larger. Category: Weeds. Erect summer annual. Anti-oxidizing Properties Pacifico et al., (2008) studied the antioxidant activity of the methanolic extract of redroot pigweed. Leaf shape Multimedia. Two pigweed species, tentatively identified as Palmer amaranth (left) and smooth pigweed (right), grow at the edge of a plastic mulched bed in organic vegetable production in Clemson, South Carolina. In the northeastern United States, Powell amaranth emerges at lower temperatures and demonstrates more tolerance for light frosts than other pigweeds (Mohler and DiTommaso, unpublished). Response of weeds to soil phosphorus and potassium. Lack of hairs. Top view of the mature leaves of a redroot pigweed, photo by Howard F. Schwartz from Colorado State University via Bigwood.org. "A Quick Pigweed Identification Exercise." • First leaves are more tapered and slightly pinched toward the end, unlike redroot and smooth pigweed. 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. If those weeds are Redroot Pigweed Amaranth. Smooth and redroot pigweed have an upright habit like Palmer amaranth and waterhemp, but both have at least slightly hairy stems. (For reference, some seedlings may penetrate 3,600 lb/acre of loose straw.). redroot pigweed or Powell amaranth. Mulch is an option in vegetable and small fruit; make sure to apply a thick and dense mulch. Seed germination in redroot and smooth pigweeds is promoted by high temperatures (86–104°F), diurnally fluctuating temperatures (e.g., 59°F / 95°F), and light (Guo and Al-Khatib, 2003; Schonbeck and Egley, 1980; Steckel et al., 2004)–stimuli which are related to proximity to the soil surface and absence of shading vegetation. (a) Inflorescence of redroot pigweed. Nitrogen fertilizer rate effects on weed competitiveness is species dependent. Uncomposted manure is a common source of pigweed seeds. 2009. Sprouted pigweed seeds can be added to salads while the tiny pigweed seeds can be roasted, crushed and used as cereal substitute. (c) Smooth pigweed inflorescence. They include such well known Iowa pests as redroot pigweed, smooth pig- weed… 2004. 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. In addition, the pigweeds: Palmer amaranth, waterhemp, redroot pigweed, Powell amaranth, and smooth pigweed, are not easily separated by species at the immature stages. Presence of hairs on the leaves, stem, and petioles indicates that it is redroot or smooth pigweed. 1991. Photo credits: (a) Joseph M. DiTomaso, University of California - Davis, Bugwood.org. Redroot and smooth pigweeds (Amaranthus retroflexus L. and A. hybridus L.) Powell amaranth (Amaranthus powellii) Various mammals, including mice, also eat Pigweed seeds. Seeds germinate spring through summer. Pigweed (Amaranthus species) are in full flower. It is a common annual weed, producing many seeds that remain viable for up to 5 years. Mohler, C. A., and A. DiTommaso. Maize and pigweed response to nitrogen supply and form. There are from 65 to 75 species of amaranths, many of which are important field weeds.

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