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Overview

Comprehensive Description

Description

This adventive plant is a summer annual about 1-3' tall that is either sparingly branched or unbranched. The central stem is stout, round, light green, and more or less covered with white hairs; it also has fine longitudinal veins that are white. The alternate leaves are up to 6" long and 4" across (excluding the petioles), becoming smaller in the upper half of the central stem. They are cordate-ovate or elliptic and smooth or slightly undulate along the margins. The base of each leaf is rounded or wedge-shaped, while its tip is rounded and blunt. The lower surface of each leaf is usually pubescent, while the upper surface is less pubescent or hairless.  The central stem terminates in a stout panicle of spikes with whitish green flowers. This terminal inflorescence is up to 6" long (rarely longer in large plants). There are also shorter axilllary panicles of flowering spikes or simple spikes that develop from the axils of the middle to upper leaves. The flowering spikes are bristly in appearance from the crowded flowers and pointed bracts. Rough Pigweed is usually monoecious with separate pistillate (female) and staminate (male) flowers on the same plant. The pistillate flowers have 5 pale white sepals, an ovary with 3 styles, and no petals. The staminate flowers have 5 pale white sepals, 5 stamens, and no petals. The sepals are oblong and about 3 mm. in length; their tips are either short and pointed or flattened. At the base of each flower, there are one or more green bracts about 3-6 mm. long. These bracts have long pointed tips. The blooming period occurs from late summer to early fall and lasts about 1-2 months. Cross-pollination of the flowers is by wind. Each pistillate flower develops a single seed in a membranous bladder (utricle). This utricle splits up to release the seed. Each small seed is dark brown or black, flattened, and circular; it has a smooth and shiny surface. The root system consists of a short stout taproot that is usually tinted red. This plant spreads by reseeding itself. Cultivation
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Distribution

National Distribution

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Range and Habitat in Illinois

Rough Pigweed is a common plant that occurs in most counties of Illinois (see Distribution Map). It is originally from South America. Habitats include dry areas of disturbed prairies, disturbed hill prairies, cropland, fallow fields, farm lots, gardens, gravelly areas along roads and railroads, sunny areas along the foundations of buildings, and waste areas. Highly disturbed areas are preferred. Faunal Associations
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Rough pigweed is found throughout North America, from Canada to Mexico,
and from the Atlantic to the Pacific coasts. It is also found
throughout much of the rest of the world, including Europe, South
America, Eurasia, and Africa. It is a native of tropical America
[11,14,18,19,27,35,43].
  • 11. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]
  • 14. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 18. Hitchcock, C. Leo; Cronquist, Arthur. 1973. Flora of the Pacific Northwest. Seattle, WA: University of Washington Press. 730 p. [1168]
  • 19. Hulten, Eric. 1968. Flora of Alaska and neighboring territories. Stanford, CA: Stanford University Press. 1008 p. [13403]
  • 27. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 35. Seymour, Frank Conkling. 1982. The flora of New England. 2d ed. Phytologia Memoirs 5. Plainfield, NJ: Harold N. Moldenke and Alma L. Moldenke. 611 p. [7604]
  • 43. Voss, Edward G. 1985. Michigan flora. Part II. Dicots (Saururaceae--Cornaceae). Bull. 59. Bloomfield Hills, MI: Cranbrook Institute of Science; Ann Arbor, MI: University of Michigan Herbarium. 724 p. [11472]

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Regional Distribution in the Western United States

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands

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Occurrence in North America

AL AK AZ AR CA CO CT DE FL GA
ID IL IN IA KS KY LA ME MD MA
MI MN MS MO MT NE NV NH NJ NM
NY NC ND OH OK OR PA RI SC SD
TN TX UT VT VA WA WV WI WY AB
BC MB NB NS ON PE PQ SK MEXICO

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Distribution in Egypt

Nile and Mediterranean regions, and Sinai.

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Global Distribution

Native of north America.

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St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; introduced and naturalized nearly worldwide.
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Distribution: A native of N. America south to N. Mexico; introduced into the Old World as a weed, but in more temperate regions than many of its allies, occurring in S. and C. Europe, Mediterranean N. Africa and temperate Asia from Cyprus and Turkey to Iran, Siberia, Middle Asia, Mongolia, China and Japan. Also adventive in Australia and S. America (Bolivia etc.) and probably elsewhere. Generally occurs as a weed of cultivation, occurring as such in the cooler parts of Pakistan, ascending to 1820 m or more.
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Physical Description

Morphology

Description

More info for the term: monoecious

Rough pigweed is an introduced, coarse, monoecious, annual herb with
taproots. It has an erect stem, 1 to 6.6 feet (0.3-2 m) tall, that is
commonly freely branched. Leaves are 0.8 to 3.9 inches (2-10 cm) long.
Inflorescences are usually densely crowded. There are often additional
dense clusters of flowers in the axils of upper leaves. The fruit is a
utricle [11,14,18,19,34].

Rough pigweed has a taproot. In pinyon-juniper (Pinus-Juniperus)
woodland in New Mexico, root depth averaged 39 inches (100 cm), with a
range of 3.9 to 95 inches (10-240 cm) [12].
  • 11. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]
  • 12. Foxx, Teralene S.; Tierney, Gail D. 1987. Rooting patterns in the pinyon-juniper woodland. In: Everett, Richard L., compiler. Proceedings--pinyon-juniper conference; 1986 January 13-16; Reno, NV. Gen. Tech. Rep. INT-215. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 69-79. [4790]
  • 14. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 18. Hitchcock, C. Leo; Cronquist, Arthur. 1973. Flora of the Pacific Northwest. Seattle, WA: University of Washington Press. 730 p. [1168]
  • 19. Hulten, Eric. 1968. Flora of Alaska and neighboring territories. Stanford, CA: Stanford University Press. 1008 p. [13403]
  • 34. Roland, A. E.; Smith, E. C. 1969. The flora of Nova Scotia. Halifax, NS: Nova Scotia Museum. 746 p. [13158]

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Description

Annual herb, erect or with ascending branches, (6-) 15-80 (-100) cm, simple or branched (especially from the base to about the middle of the stem). Stem stout, sub-terete to angled, densely furnished with multicellular hairs. Leaves furnished with multicellular hairs along the lower surface of the primary venation and often the lower margins, long-petiolate (petioles up to c. 6 cm, in robust plants not rarely equalling the lamina), lamina ovate to rhomboid or oblong-ovate, (1-) 5-11 x (0.6-) 3-6 cm, obtuse to subacute at the mucronulate tip, shortly cuneate or attenuate into the petiole. Flowers in greenish or rarely somewhat pink-suffused, stout, axillary and terminal spikes, which are usually shortly branched to give a lobed appearance, more rarely with longer branches, the terminal inflorescence paniculate, very variable in size, male and female flowers intermixed, the latter generally much more plentiful except sometimes at the tip of the spikes. Bracts and bracteoles lanceolate-subulate, pale-membranous with a prominent green midrib excurrent into a stiff, colourless arista, longer bracteoles subequalling to twice as long as the perianth. Perianth segments 5, those of the male flowers 1.75-2.25 mm, lanceolate-oblong, blunt to subacute, those of the female flowers 2-3 mm, narrowly oblong-spathulate to spathulate, obtuse or emarginate, ± green-vittate along the midrib, which ceases below the apex or is excurrent in a short mucro. Stigmas 2-3, patent-flexuose or erect, c. 1 mm. Capsule subglobose, c. 2 mm, usually shorter than the perianth, circumscissile, with an indistinct neck, rugose below the lid. Seed black and shining, compressed, c. 1 mm, almost smooth centrally, faintly reticulate around the margins.
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Description

Stem erect, light green, 20-80 cm tall, stout, branched or not, slightly obtusely angulate, densely pubescent. Petiole light green, 1.5-5.5 cm, hairy; leaf blade ovate-rhombic or elliptic, 5-12 × 2-5 cm, both surfaces shortly hairy, but densely hairy abaxially, base cuneate, margin entire and undulate, apex acute or notched, with a mucro. Complex thyrsoid structures terminal and axillary, erect, 2-4 cm in diam., including many spikes; terminal spikes longer than lateral ones. Bracts and bracteoles white, subulate, 4-6 mm, apex slenderly long pointed. Tepals white, oblong or oblong-obovate, 2-2.5 mm, membranous, with a green midvein, apex acute or notched, with a mucro. Stamens slightly longer than perianth. Stigmas 3, rarely 2. Utricles light green, ovoid, compressed, shorter than perianth, circumscissile. Seeds brown or black, subglobose, ca. 1 mm in diam., obtuse at margin. Fl. Jul-Aug, fr. Aug-Sep. 2n = 32*, 34*, 102*.
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Description

Plants densely to moderately pubescent, especially distal parts of stem and branches. Stems erect, reddish near base, branched in distal part to simple 0.2-1.5(-2) m; underdeveloped or damaged plants rarely ascending to nearly prostrate. Leaves: petiole 1/2 to equaling blade; blade ovate to rhombic-ovate, 2-15 × 1-7 cm, base cuneate to rounded-cuneate, margins entire, plane or slightly undulate, apex acute, obtuse, or slightly emarginate, with terminal mucro. Inflorescences terminal and axillary, erect or reflexed at tip, green or silvery green, often with reddish or yellowish tint, branched, leafless at least distally, usually short and thick. Bracts lanceolate to subulate, (2.5-)3.5-5(-6) mm, exceeding tepals, apex acuminate with excurrent midrib. Pistillate flowers: tepals 5, spatulate-obovate, lanceolate-spatulate, not clawed, subequal or unequal, (2-)2.5-3.5(-4) mm, membranaceous, apex emarginate or obtuse, with mucro; style branches erect or slightly spreading,; stigmas 3. Staminate flowers few at tips of inflorescences; tepals 5; stamens (3-)4-5. Utricles broadly obovoid to broadly elliptic, 1.5-2.5 mm, shorter than or subequal to tepals, smooth or slightly rugose, especially near base and in distal part, dehiscence regularly circumscissile. Seeds black to dark reddish brown, lenticular to subglobose-lenticular, 1-1.3 mm, smooth, shiny.
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Diagnostic Description

Synonym

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Ecology

Habitat

Range and Habitat in Illinois

Rough Pigweed is a common plant that occurs in most counties of Illinois (see Distribution Map). It is originally from South America. Habitats include dry areas of disturbed prairies, disturbed hill prairies, cropland, fallow fields, farm lots, gardens, gravelly areas along roads and railroads, sunny areas along the foundations of buildings, and waste areas. Highly disturbed areas are preferred. Faunal Associations
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Habitat characteristics

Rough pigweed grows in cultivated fields, gardens, orchards, fallow
land, stream valleys, shores, prairie ravines, roadsides, fence rows,
and waste places [17,34,35,43,47]. Its grows in dry to moist conditions
[7].

In Utah, rough pigweed demonstrated poor growth on gravel, dense clay,
and sodic-saline soils; fair growth on sandy, clay-loam, organic acidic,
and saline soils; and good growth on sandy loam, loam, and clay.
Optimum soil depth was 10 to 20 inches (25-50 cm) [7].

Recorded elevations for rough pigweed are [7]:

State Elevation (feet) Elevation (m)

Arizona 5,000-7,000 1,525-2,134
Colorado 4,700-9,200 1,433-2,804
Montana 2,300-9,000 700-2,743
Utah 4,400-4,700 1,341-1,433
Wyoming 4,300-7,800 1,310-2,377
  • 17. Harrington, H. D. 1964. Manual of the plants of Colorado. 2d ed. Chicago: The Swallow Press Inc. 666 p. [6851]
  • 34. Roland, A. E.; Smith, E. C. 1969. The flora of Nova Scotia. Halifax, NS: Nova Scotia Museum. 746 p. [13158]
  • 35. Seymour, Frank Conkling. 1982. The flora of New England. 2d ed. Phytologia Memoirs 5. Plainfield, NJ: Harold N. Moldenke and Alma L. Moldenke. 611 p. [7604]
  • 43. Voss, Edward G. 1985. Michigan flora. Part II. Dicots (Saururaceae--Cornaceae). Bull. 59. Bloomfield Hills, MI: Cranbrook Institute of Science; Ann Arbor, MI: University of Michigan Herbarium. 724 p. [11472]
  • 47. Welsh, Stanley L.; Atwood, N. Duane; Goodrich, Sherel; Higgins, Larry C., eds. 1987. A Utah flora. Great Basin Naturalist Memoir No. 9. Provo, UT: Brigham Young University. 894 p. [2944]
  • 7. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]

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Habitat: Cover Types

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

Rough pigweed occurs in most SAF Cover Types

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Habitat: Plant Associations

More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

Rough pigweed occurs in most Kuchler Plant Associations

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Habitat: Ecosystem

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

Rough pigweed occurs in most ecosystems

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Weeds of cultivation and naturalized.

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Banks of rivers, lakes, and streams, disturbed habitats, agricultural fields, railroads, roadsides, waste areas; 0-2500m.
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Habitat & Distribution

Waste places, field margins, roadsides. Gansu, Hebei, Heilongjiang, Jilin, Liaoning, Nei Mongol, Ningxia, Shaanxi, Shandong, Shanxi, Xinjiang, Zhejiang [native origin uncertain; now cosmopolitan].
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Associations

In Great Britain and/or Ireland:
Foodplant / parasite
sorus of Albugo bliti parasitises live leaf of Amaranthus retroflexus

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General Ecology

Successional Status

More info on this topic.

More info for the term: competition

Obligate Initial Community Species

Rough pigweed, an early successional species, extracts more nitrogen
from and grows faster on the nitrogen-poor soils of recently abandoned
fields than mid- and late successional species [38].

In Michigan, an agricultural field was rototilled and abandoned in
March. By May, seedlings of several annuals had emerged. Dominant
species during the first growing season included rough pigweed. In
similar adjacent fields that had been abandoned for 5 and 15 years,
rough pigweed was not present. [16].

During the 1934 drought, rough pigweed grew thickly where windblown dust
had covered considerable portions of prairies in Kansas and Nebraska.
Rough pigweed and other ruderals normally not found in prairies became
widely distributed when released from their usual competition with
grasses. However, with the end of drought and the return of grasses,
rough pigweed nearly disappeared in many prairies [45].
  • 16. Gross, Katherine L.; Werner, Patricia A. 1982. Colonizing abilities of "biennial" plant species in relation to ground cover: implications for their distributions in a successional sere. Ecology. 63(4): 921-931. [12143]
  • 38. Tilman, David. 1986. Nitrogen-limited growth in plants from different successional stages. Ecology. 67(2): 555-563. [2809]
  • 45. Weaver, J. E.; Albertson, F. W. 1944. Nature and degree of recovery of grassland from the great drought of 1933-1940. Ecological Monographs. 14(4): 393-479. [2462]

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Growth Form (according to Raunkiær Life-form classification)

More info on this topic.

More info for the term: therophyte

Therophyte

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Life Form

More info for the term: forb

Forb

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Post-fire Regeneration

Ground residual colonizer (on-site, initial community)
Initial-offsite colonizer (off-site, initial community)

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Plant Response to Fire

When rough pigweed is killed by fire, the population must establish from
seed. If a fire in the spring kills rough pigweed plants but
conditions continue to be favorable, seeds from the seedbank will
germinate [44]. Late in the growing season, a fire will prepare the
seedbed for establishment of rough pigweed from seed the next spring.
  • 44. Whitson, Tom D., ed. 1987. Weeds and poisonous plants of Wyoming and Utah. Res. Rep. 116-USU. Laramie, WY: University of Wyoming, College of Agriculture, Cooperative Extension Service. 281 p. [2939]

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Fire Ecology

Rough pigweed seeds are an important part of the seedbank in many
habitats, even when plants are almost absent [16]. As an obligate
initial community species, rough pigweed needs bare, disturbed sites in
order to establish [26,38]. A fire which clears away competing
vegetation can allow the establishment of rough pigweed.

Rough pigweed seeds are very small [14], and easily blown by the wind
from off-site sources. Some seeds survive cattle digestion [4], and can
be carried by animals to burned areas.
  • 14. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 16. Gross, Katherine L.; Werner, Patricia A. 1982. Colonizing abilities of "biennial" plant species in relation to ground cover: implications for their distributions in a successional sere. Ecology. 63(4): 921-931. [12143]
  • 26. McConnaughay, K. D. M.; Bazzaz, F. A. 1987. The relationship between gap size and performance of several colonizing annuals. Ecology. 68(2): 411-416. [2869]
  • 38. Tilman, David. 1986. Nitrogen-limited growth in plants from different successional stages. Ecology. 67(2): 555-563. [2809]
  • 4. Blackshaw, Robert E.; Rode, Lyle M. 1991. Effect of ensiling and rumen digestion by cattle on weed seed viability. Weed Science. 39(1): 104-108. [21835]

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Regeneration Processes

Rough pigweed regenerates from seed each year. Plants can result from
germination of newly released seed, or from germination of seed carried
over in the seedbank from previous years. Seeds may germinate any time
soil moisture is adequate during the growing season [44].

Rough pigweed seeds harvested in Mississippi showed 94 percent viability
at time of harvest. After burial in soil for 30 months, seeds showed 7
percent viability. Seeds put in dry, low-temperature storage for 30
months had 98 percent viability [8].

Some seeds of rough pigweed remained viable after 24 hours of rumen
digestion, 8 weeks ensiling, or both [4].
  • 4. Blackshaw, Robert E.; Rode, Lyle M. 1991. Effect of ensiling and rumen digestion by cattle on weed seed viability. Weed Science. 39(1): 104-108. [21835]
  • 44. Whitson, Tom D., ed. 1987. Weeds and poisonous plants of Wyoming and Utah. Res. Rep. 116-USU. Laramie, WY: University of Wyoming, College of Agriculture, Cooperative Extension Service. 281 p. [2939]
  • 8. Egley, G. H.; Chandler, J. M. 1978. Germination and viability of weed seeds after 2.5 years in a 50-year buried seed study. Weed Science. 26(3): 230-239. [19609]

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Life History and Behavior

Cyclicity

Phenology

More info on this topic.

Rough pigweed normally begins growth in late spring and matures in late
summer or early fall [44]. It blooms in the Great Plains from July to
October [14], and in the central and northeastern United States and
adjacent Canada from August to October [11]. It blooms in southern
California from June to November [27], in Montana from June to October,
in North Dakota and Wyoming from July to September [7] and in the
Carolinas from July until frost [31].
  • 11. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]
  • 14. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 27. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 31. Radford, Albert E.; Ahles, Harry E.; Bell, C. Ritchie. 1968. Manual of the vascular flora of the Carolinas. Chapel Hill, NC: The University of North Carolina Press. 1183 p. [7606]
  • 44. Whitson, Tom D., ed. 1987. Weeds and poisonous plants of Wyoming and Utah. Res. Rep. 116-USU. Laramie, WY: University of Wyoming, College of Agriculture, Cooperative Extension Service. 281 p. [2939]
  • 7. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]

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Flowering/Fruiting

Flowering summer-fall.
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Life Expectancy

Annual.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Amaranthus retroflexus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 22
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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Management

Management considerations

More info for the terms: cover, forb

Rough pigweed is a useful component of patchwork vegetation for scaled
quail habitat, providing both food and cover [1].

Rough pigweed is difficult to eradicate when once established [34]. A
survey of weeds in spring annual crops throughout Manitoba over a 4-year
period showed 83 weed species. Rough pigweed was the third most common
dicotyledonous weed [40]. In Kansas, it was the most abundant forb weed
in the seedbank [24].

Rough pigweed can be controlled with herbicides [30].

Cultivation reduces longevity of rough pigweed seed, apparently by
increasing soil aeration, exposing the seeds to light, and generally
improving conditions for germination. High soil temperatures favor
germination and reduce rough pigweed seed survival [8].

Rough pigweed showed no establishment in intact prairie vegetation in an
Illinois study. It did, however, establish in gaps in prairie
vegetation. Flowering and seed set increased with increasing gap size
[26].

An investigation was conducted in Nebraska as to the effect of cattle
grazing in controlling rough pigweed and other weeds in seeded
grassland. Cattle consumed immature rough pigweed, but nitrate
accumulation limited grazing rough pigweed as a weed control practice
[23].
  • 1. Ault, Stacey C.; Stormer, Fred A. 1983. Seasonal food selection by scaled quail in northwest Texas. Journal of Wildlife Management. 47(1): 222-228. [12168]
  • 23. Lawrence, B. K.; Waller, S. S.; Moser, L. E.; [and others]
  • 24. Lippert, Robert D.; Hopkins, Harold H. 1950. Study of viable seeds in various habitats in mixed prairie. Transactions of the Kansas Academy of Science. 53(3): 355-364. [1461]
  • 26. McConnaughay, K. D. M.; Bazzaz, F. A. 1987. The relationship between gap size and performance of several colonizing annuals. Ecology. 68(2): 411-416. [2869]
  • 30. Peterson, D. E.; Regehr, D. L.; Ohlenbusch, P. D.; [and others]
  • 34. Roland, A. E.; Smith, E. C. 1969. The flora of Nova Scotia. Halifax, NS: Nova Scotia Museum. 746 p. [13158]
  • 40. Thomas, A. G.; Donaghy, D. I. 1991. A survey of the occurrence of seedling weeds in spring annual crops in Manitoba. Canadian Journal of Plant Science. 71(3): 811-820. [21781]
  • 8. Egley, G. H.; Chandler, J. M. 1978. Germination and viability of weed seeds after 2.5 years in a 50-year buried seed study. Weed Science. 26(3): 230-239. [19609]

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These species are introduced in Switzerland.
  • Aeschimann, D. & C. Heitz. 2005. Synonymie-Index der Schweizer Flora und der angrenzenden Gebiete (SISF). 2te Auflage. Documenta Floristicae Helvetiae N° 2. Genève.   http://www.crsf.ch/ External link.
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© Info Flora (CRSF/ZDSF) & Autoren 2005

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Relevance to Humans and Ecosystems

Benefits

Other uses and values

More info for the term: fresh

Young leaves of rough pigweed are used as salad greens when the plant is
only a few inches tall, before the stem becomes woody. Fresh young
plants can also be used as a potherb. Seeds are edible whole or ground
into meal. However, because rough pigweed concentrates nitrates, it
should be used in moderation, particularly when taken from
nitrate-fertilized areas [9].
  • 9. Elias, Thomas S.; Dykeman, Peter A. 1982. Field guide to North American edible wild plants. [Place of publication unknown]

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Cover Value

More info for the term: cover

The degree to which rough pigweed provides environmental cover for
wildlife species in several western states is as follows [7]:

North
Dakota Utah Wyoming

Pronghorn good poor poor
Elk poor poor
Mule deer good poor poor
White-tailed deer good poor
Small mammals fair fair
Small nongame birds fair fair
Upland game birds poor poor poor
Waterfowl fair poor poor
  • 7. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]

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Importance to Livestock and Wildlife

More info for the terms: fresh, presence

Rough pigweed affects the kidneys of swine and cattle when animals
consume large quantities of fresh material for 5 to 10 days. Cattle
have developed perirenal edema and toxic nephrosis after ingesting rough
pigweed. The toxicant has not been identified, although oxalates and/or
phenolics have been suspected [37]. Additionally, rough pigweed
accumulates nitrates, which causes poisoning in most livestock species
when ingested in large quantities either fresh or in hay [6,21,44]. The
excess nitrates cause cattle to bloat [41]. In the Midwest, pigs have
been poisoned by rough pigweed growing under drought stress. In drought
conditions, rough pigweed accumulation of nitrates accelerates [28,49].

In Nebraska, cattle consumed immature leaves and tops of rough pigweed
in fields seeded to big bluestem (Andropogon gerardii var. gerardii).
By mid-July of the first year of the study, nitrate concentration had
reached toxic levels (10,000 ppm). In the second year, nitrate levels
exceeded the toxic level at the beginning of the grazing season [23].

Sheep in Texas were maintained for varying lengths of time on rough
pigweed pasture supplemented with wheat and alfalfa hays [15].

Scaled quail in Texas made use of rough pigweed seeds. When available,
seeds averaged 0.9 percent of food eaten. In the highest recorded use,
rough pigweed seeds made up 3.6 percent of food eaten. Percent use was
greater than rough pigweed presence [1].
  • 1. Ault, Stacey C.; Stormer, Fred A. 1983. Seasonal food selection by scaled quail in northwest Texas. Journal of Wildlife Management. 47(1): 222-228. [12168]
  • 15. Griggs, T. C.; Matches, A. G. 1991. Crop ecology, production, and management: Productivity and consumption of wheatgrasses and wheatgrass-sainfoin mixtures grazed by sheep. Crop Science. 31(5): 1267-1273. [18055]
  • 21. Kingsbury, John M. 1964. Poisonous plants of the United States and Canada. Englewood Cliffs, NJ: Prentice-Hall, Inc. 626 p. [122]
  • 23. Lawrence, B. K.; Waller, S. S.; Moser, L. E.; [and others]
  • 28. Nabhan, Gary Paul. 1985. Gathering the desert. Tucson, AZ: The University of Arizona Press. 209 p. [2848]
  • 37. Sturart, B. P.; Nicholson, S. S.; Smith, J. B. 1975. Perirenal edema and toxic nephrosis in cattle, associated with ingestion of pigweed. Journal of the American Veterinary Medicine Association. 167(10): 949-950. [21782]
  • 41. U.S. Department of Agriculture, Agricultural Research Service. 1971. Common weeds of the United States. New York: Dover Publications, Inc. 463 p. [2378]
  • 44. Whitson, Tom D., ed. 1987. Weeds and poisonous plants of Wyoming and Utah. Res. Rep. 116-USU. Laramie, WY: University of Wyoming, College of Agriculture, Cooperative Extension Service. 281 p. [2939]
  • 49. Wohlgemuth, K.; Schamber, G. J.; Misek, A. R.; Crenshaw, J. D. 1987. Pigweed is toxic to pigs. North Dakota Farm Research. Fargo, ND: North Dakota Agricultural Experiment Station; 44(4): 21-22. [21836]
  • 6. Burrows, George E.; Tyrl, Ronald J.; Rollins, Dale;. [and others]

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Nutritional Value

Rough pigweed seeds with hulls contain 18.0 percent protein [29].

The nutritional components of immature rough pigweed browse are [29]:

Component Percent

Ash 18.8
Crude Fiber 10.8
N-free Extract 43.2
Protein 25.7

The use that various animals can make of protein in rough pigweed browse
is [29]:

Percent
Animal Digestible Protein

Cattle 19.7
Goats 20.5
Horses 19.3
Rabbits 18.5
Sheep 20.9

The food value of rough pigweed for wildlife species in several western
states is rated as follows [7]:

North
Dakota Utah Wyoming

Pronghorn good fair poor
Elk fair poor
Mule deer good good poor
White-tailed deer good poor
Small Mammals fair good
Small nongame birds good good
Upland game birds good fair good
Waterfowl good poor fair

In Minnesota, rough pigweed harvested from late June to mid-July showed
a nutrient composition and digestibility for sheep equivalent to that of
high-quality alfalfa (Medicago sativa). Rough pigweed contained
adequate minerals to meet the requirements of ruminants. However, it
must be utilized at relatively early stages of maturity. Nitrate
concentration, which has been implicated in livestock poisoning, is
highest in rough pigweed just before bloom. Calcium to potassium ratio
in rough pigweed is such that it should not be fed as the sole ration
[25].
  • 25. Marten, G. C.; Andersen, R. N. 1975. Forage nutritive value and palatability of 12 common annual weeds. Crop Science. 15: 821-827. [25]
  • 29. National Academy of Sciences. 1971. Atlas of nutritional data on United States and Canadian feeds. Washington, DC: National Academy of Sciences. 772 p. [1731]
  • 7. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]

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Palatability

Rough pigweed is probably unpalatable when mature because of the stiff,
spine-like bracts in the flower clusters.

In Utah, rough pigweed was rated as having fair palatability for cattle
and horses, and good palatability for sheep [7].

In Minnesota, rough pigweed was as palatable to sheep as oats (Avena
sativa) [25].
  • 25. Marten, G. C.; Andersen, R. N. 1975. Forage nutritive value and palatability of 12 common annual weeds. Crop Science. 15: 821-827. [25]
  • 7. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]

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Wikipedia

Amaranthus retroflexus

Amaranthus retroflexus is a species of flowering plant in the Amaranthaceae family with several common names, including red-root amaranth, redroot pigweed, red-rooted pigweed, common amaranth, pigweed amaranth, and common tumbleweed.[3]

Description[edit]

Amaranthus retroflexus, true to one of its common names, forms a tumbleweed.[3] It is native to the tropical Americas, but is widespread as an introduced species on most continents in a great number of habitats. This is an erect, annual herb reaching a maximum height near 3 m. The leaves are nearly 15 cm long on large individuals, the ones higher on the stem having a lance shape and those lower on the plant diamond or oval in shape. The plant is monoecious, with individuals bearing both male and female flowers. The inflorescence is a large, dense cluster of flowers interspersed with spiny green bracts. The fruit is a capsule less than 2 mm long with a "lid" which opens to reveal a tiny black seed. Another of A. retroflexus's common names, pigweed, stems from the fact that it grows where hogs are pasture-fed.

Culinary use[edit]

Southern Kerala-style traditional thoran made with cheera (A. retroflexus) leaves

This plant is eaten as a vegetable in different places of the world. No species of genus Amaranthus is known to be poisonous,[4] but the leaves contain oxalic acid and may contain nitrates if grown in nitrate-rich soils, so the water should be discarded after boiling.

A. retroflexus was used for a multitude of food and medicinal purposes by many Native American groups.[5]

It is used in the Indian state of Kerala to prepare a popular dish known as thoran by combining the finely cut leaves with grated coconut, chili peppers, garlic, turmeric and other ingredients.

The seeds are edible raw or toasted, and can be ground into flour and used for bread, hot cereal, or as a thickener.[6]

Use as fodder[edit]

Like many other species of Amaranthus, this plant may be harmful and even deadly when fed to cattle and pigs in large amounts over several days. Such forage may cause fatal nephrotoxicity,[7] presumably because of its high oxalate content. Other symptoms, such as bloat, might reflect its high nitrate content.[8] However, when supplied in moderation, it is regarded as an exceptionally nutritious fodder.[9]

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Notes

Comments

Amaranthus retroflexus, native to central and eastern North America, is a successful invasive species and has effectively colonized a wide range of habitats on all inhabited continents. Its variability is extremely wide; usually the species is easily recognized and its identification causes no specific problems. Infraspecific entities described within A. retroflexus are mostly ecologic variants of little or no taxonomic value. Two varieties are more easily recognized: the common var. retroflexus, with bracts about 1.5-2 times as long as tepals, and a more rare var. delilei (Richter & Loret) Thellung (= A. delilei Richter & Loret), with bracts 1-1.5 times as long as tepals. 

 Occasional forms morphologically intermediate between Amaranthus retroflexus and taxa of the A. hybridus aggregate (e.g., A. powellii and A. hybridus, in the strict sense) are known both in the Americas and the Old World. Usually such plants are treated as hybrids; in many cases they are probably just extremes of the natural variability of A. retroflexus. Putative hybrids of A. retroflexus were described from Europe as A. ×ozanonii Thellung (A. hybridus × A. retroflexus) and A. ×soproniensis Priszter & Karpáti (A. powellii × A. retroflexus) (see A. Thellung 1914-1919; S. Priszter 1958; P. Aellen 1959; F. Grüll and S. Priszter 1973).

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Comments

One of us (Clemants) does not recognize the following varieties.
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Names and Taxonomy

Taxonomy

Common Names

rough pigweed
redroot pigweed
redroot amaranth
green amaranth
pigweed
wild beet
pigweed amaranth
canne
red-root pigweed
careless weed

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The currently accepted scientific name of rough pigweed is Amaranthus
retroflexus L. [11,14,18,20]. It is a member of the pigweed family
(Amaranthaceae). There are no recognized subspecies, varieties, or
forms.
  • 11. Fernald, Merritt Lyndon. 1950. Gray's manual of botany. [Corrections supplied by R. C. Rollins]
  • 14. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 18. Hitchcock, C. Leo; Cronquist, Arthur. 1973. Flora of the Pacific Northwest. Seattle, WA: University of Washington Press. 730 p. [1168]
  • 20. Kartesz, John T.; Kartesz, Rosemarie. 1980. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. Volume II: The biota of North America. Chapel Hill, NC: The University of North Carolina Press; in confederation with Anne H. Lindsey and C. Richie Bell, North Carolina Botanical Garden. 500 p. [6954]

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