Search
Advanced Search
MT Gov Logo
MONTANA FIELD GUIDE™

MONTANA FIELD GUIDE™

Redroot Amaranth - Amaranthus retroflexus

Image Copyright and Usage Information
Native Species

Global Rank: G5
State Rank: SNR
(see State Rank Reason below)
C-value: 2


Agency Status
USFWS:
USFS:
BLM:


 





State Rank Reason (see State Rank above)
Native to parts of eastern and central North America and introduced into Montana. This is the most abundant pigweed in the state.
 
General Description
Monoecious. Stems erect, reddish below, 10–100 cm with sparsely pubescent foliage. Leaf blade lanceolate to ovate, 2–10 cm long, just longer than petiole. Inflorescence often red-tinged, dense, terminal and axillary panicles; bracts lanceolate-attenuate, 3–5 mm long, short-pointed. Flowers: sepals 5, ca. 3 mm long with blunt to rounded tips and excurrent midveins; stamens 4 to 5. Utricle ca. 2 mm, nearly as long as sepals (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Diagnostic Characteristics
Redroot Amaranth - Amaranthus retroflexus, native
* Plants: Staminate and pistillate flowers on the same plant (monoecious). Central stem, reddish below, and often less than 3 feet tall.
* Hairs: soft and short (pubescent) on the stem, giving the plant a fuzzy appearance.
* Leaves: Petiole shorter than blade. Blade obovate in shape, 2-10 cm long.
* Inflorescence: Relatively short and thick, with short, pointed bracts.

Palmer's Amaranth - Amaranthus palmeri, non-native, invasive, and undesirable
* Plants: Staminate and pistillate flowers on separate plants (dioecious). Central stem, reddish-green, and often at least 3 feet tall.
* Hairs: Hairs absent (glabrous).
* Leaves: Petiole longer than blade. Lanceolate when young, becoming more obovate with maturity.
* Inflorescence: Relatively long and narrow, and terminal or in axils of leaves.

Prostrate Amaranth - Amaranthus blitoides, native
* Plants: Staminate and pistillate flowers on the same plant (monoecious). Stems branched and prostrate, often less than 1.5 feet tall.
* Hairs: Glabrous to pubescent.
* Leaves: Petiole barely longer than blade. Lanceolate to ovate, 10-25 mm long.
* Inflorescence: Shorter flowering stems.

Species Range
Montana Range Range Descriptions
Range in Montana
CC BY NC
Native
 


Range Comments
Known from nearly every MT county; throughout North America (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 124
(Click on the following maps and charts to see full sized version)
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Cultivated fields, roadsides, stream banks; plains, valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).


References
  • Literature Cited AboveLegend:   View Online Publication
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Adhikari, S. 2018. Impacts of dryland farming systems on biodiversity, plant-insect interactions, and ecosystem services. Ph.D. Dissertation. Bozeman, MT: Montana State University. 207 p.
    • Adhikari, S., L.A. Burkle, K.M. O'Neill, C.M. Delphia, D.K. Weaver, and F.D. Menalled. 2019. Dryland organic farming partially offsets negative effects of highly simplified agricultural landscapes on forbs, bees, and bee-flower networks. Environmental Entomology 48(4): 826-835.
    • Eggers, M.J.S. 2005. Riparian vegetation of the Montana Yellowstone and cattle grazing impacts thereon. M.Sc. Thesis. Montana State University, Bozeman, MT. 125 p.
    • Harvey, S.J. 1990. Responses of steppe plants to gradients of water soil texture and disturbance in Montana, U.S.A. Ph.D. Thesis. Bozeman, MT: Montana State University. 34 p.
    • Jones, W. W. 1901. Preliminary flora of Gallatin County. M.S. Thesis. Bozeman, MT: Montana State College. 78 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Martinka, R.R. 1970. Structural characteristics and ecological relationships of male blue grouse (Dendragapus obscurus (Say)) territories in southwestern Montana. Ph.D Dissertation. Bozeman, MT: Montana State University. 73 p.
    • Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
    • Sater, S. 2022. The insects of Sevenmile Creek, a pictorial guide to their diversity and ecology. Undergraduate Thesis. Helena, MT: Carroll College. 242 p.
    • Seipel, T.F. 2006. Plant species diversity in the sagebrush steppe of Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 87 p.
    • Sirirugsa, P. 1973. Descriptive analysis of Montana species of Amaranthus. M.Sc. Thesis. Bozeman, MT: Montana State University. 56 p.
    • Zapatka, T.P. 1963. Some results of two limited hunting seasons on hen Pheasants in north central Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 26 p.
  • Web Search Engines for Articles on "Redroot Amaranth"
Login Logout

Take us with you! PDF icon

Look for this PDF icon as you search and browse.  Click it to build a custom PDF with species shown on that page or for all the species within that taxonomic level.  To create your own list of species, use the PDF Creator tool at the bottom of the Advanced Search page.

Here's some links if you want to download a whole group.

Mammals
Birds
Reptiles
Amphibians
Fish
Invertebrates
Butterflies / Moths
Dragonflies / Damselflies
Ferns and allies
Conifers
Flowering Plants (Dicots)
Flowering Plants (Monocots)
Bryophytes
Lichens
Ecological Systems
Noxious Weeds
Citation for data on this website:
Redroot Amaranth — Amaranthus retroflexus.  MONTANA FIELD GUIDE™.  .  Retrieved on , from