Guilleminea densa var. aggregata
Small matweed, Small Matweed
Family: Amaranthaceae · Type: Herb · Not Native
Guilleminea densa var. aggregata (Small matweed) is a non-native California herb in the Amaranthaceae family, recognized by Only Guilleminea species in California, South American introduction.
Small matweed is a naturalized perennial found in southern Central and Southern California coastal areas on roadsides and disturbed areas at elevations below 100 meters. Flowering from August to November, this plant produces tiny white flowers in small clusters 2 to 3 millimeters wide. Growing as dense mats 10 to 80 centimeters wide with stems that are densely woolly, it spreads across disturbed ground in low-lying areas. Its leaves form basal rosettes with oblong to lanceolate blades 20 to 40 millimeters long, woolly on the undersides and glabrous on top. The plant produces small reddish-brown seeds enclosed within a persistent white-scarious perianth.
Identification and appearance
Key characters: Only Guilleminea species in California, South American introduction
Habitat and range
Habitat: Roadsides, disturbed areas
Elevation: < 100 m
Outside California: native Arizona to Texas, South America
Bloom period
Guilleminea densa var. aggregata blooms Aug-Nov.
How to tell it apart
vs Amaranthus: Amaranthus grows upright with alternate leaves; Guilleminea forms flat ground-hugging mats with opposite leaves.; vs Alternanthera: Alternanthera has swollen stems and grows near water; Guilleminea has thin stems in dry disturbed ground.; vs Nitrophila: Nitrophila has thick succulent leaves; Guilleminea has thin, flat leaves.; vs Tidestromia: Tidestromia is densely woolly-fuzzy all over; Guilleminea is smooth or nearly so.
Frequently asked questions
Is Guilleminea densa var. aggregata native to California?
No. Guilleminea densa var. aggregata is not native to California (recorded as not native).
When does Guilleminea densa var. aggregata bloom?
Guilleminea densa var. aggregata blooms Aug-Nov.
What plant family does Guilleminea densa var. aggregata belong to?
Guilleminea densa var. aggregata is in the Amaranthaceae family, genus Guilleminea.
What habitat does Guilleminea densa var. aggregata grow in?
Guilleminea densa var. aggregata grows in Roadsides, disturbed areas.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.