Amaranthus retroflexus
Redroot pigweed, Redroot Pigweed
(c) Matt Lavin, some rights reserved (CC BY-SA) · licence
Family: Amaranthaceae · Type: Herb · Not Native
Amaranthus retroflexus (Redroot pigweed) is a non-native California herb in the Amaranthaceae family, recognized by . Key features: densely woolly, short thick lateral branches, overlapping reflexed perianth parts.
Redroot pigweed is a naturalized annual found in agricultural fields and disturbed areas across the North Coast, North Coast Interior, Central Valley, Central Western, Southwestern, and Southeastern desert regions of California at elevations up to 2,400 meters. Flowering from June to November, this plant produces small green flowers in dense, erect, panicle-like clusters that can be green or silver-green in color. Growing with robust erect stems 15 to 150 centimeters tall, the plant can be either green or reddish and is densely to moderately woolly in texture. Its leaves are broadly ovate to rhombic-ovate, 20 to 150 millimeters long with wedge-shaped bases and obtuse to acute tips, attached to petioles 25 to 80 millimeters long. The fruit is a small circumscissile capsule 1.7 to 2.5 millimeters long, containing dark brown to black shiny seeds.
Identification and appearance
Key characters: 16 sympatric species. Key features: densely woolly, short thick lateral branches, overlapping reflexed perianth parts
Habitat and range
Habitat: Agricultural fields, disturbed areas
Elevation: < 2400 m
California counties: Santa Clara, San Joaquin, Stanislaus, Riverside, Orange, Los Angeles, San Bernardino, San Luis Obispo, Fresno, Kern, San Diego, Santa Barbara, Ventura, Mendocino, Lake, Contra Costa, Sonoma, Amador, Butte, Santa Cruz, San Francisco, Alpine, Madera, Yolo, Sutter, Mono, Modoc, Sacramento, San Benito, San Mateo, Yuba, Napa, Humboldt, Alameda, Tulare, Inyo, Solano, Marin, Plumas, Sierra, Calaveras, Merced, Monterey, Imperial
Outside California: native to central and eastern North America, cosmopolitan weed
Bloom period
Amaranthus retroflexus blooms Jun-Nov.
How to tell it apart
vs Celosia: Amaranthus has bristly flower spikes; Celosia has showy velvety flower plumes or crested combs.; vs Rumex: Amaranthus has dense bristly flower clusters; Rumex has flowers in whorls along stems with papery wings on fruits.; vs Salsola: Amaranthus has soft oval leaves and clustered flowers; Salsola has spine-tipped leaves and papery winged fruits.; vs Euphorbia: Amaranthus lacks milky sap and has separate male/female flowers; Euphorbia has milky sap and cup-like flower clusters.; vs Chenopodium: Amaranthus has bristly flower clusters; Chenopodium has mealy-coated leaves and flowers in loose balls.
Frequently asked questions
Is Amaranthus retroflexus native to California?
No. Amaranthus retroflexus is not native to California (recorded as not native).
When does Amaranthus retroflexus bloom?
Amaranthus retroflexus blooms Jun-Nov.
Where in California does Amaranthus retroflexus grow?
Amaranthus retroflexus occurs in Santa Clara, San Joaquin, Stanislaus, Riverside, Orange, Los Angeles, San Bernardino, San Luis Obispo and other counties, at elevations of < 2400 m.
What plant family does Amaranthus retroflexus belong to?
Amaranthus retroflexus is in the Amaranthaceae family, genus Amaranthus.
What habitat does Amaranthus retroflexus grow in?
Amaranthus retroflexus grows in Agricultural fields, disturbed areas.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.