Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Guilleminea densa, Small Matweed

Guilleminea densa, Small Matweed, Southwest Desert Flora Guilleminea densa, Small Matweed, Southwest Desert Flora

Scientific Name: Guilleminea densa
Common Name: Small Matweed
Also Called: Matweed
Family: Amaranthaceae, Pigweed Family
Synonyms: (Illecebrum densum, Brayulinea densa)
Status: Native
Duration: Perennial
Size: Up to 2 inches, 12 or more inches wide.
Growth Form: Forb/herb woolly, prostrate, mat forming along the ground, stems numerous from strong taproots.
Leaves: Shiny green; opposite, basal rosettes, petiolate, paired leaves of unequal size, oblong or ovate, tips of leaves pointed, glabrous on upper leaf surface and matted white hairs on lower surfaces.
Flower Color: White; flowers with sepals only, flowers in irregular clusters in leaf axils, bracts present, seeds red or brown.
Flowering Season: May to October
Elevation: 2,500 to 6,000 feet.

Habitat Preferences: Various habitats in mid- to high-elevations, open areas, grasslands, pinyon-juniper and oak-woodland areas and disturbed areas.

Recorded Range: Primarily in the southwestern United States in CA, AZ, CO, NM, TX, OK, MD and SC. Introduced in MD and SC. Also found in northern and central Mexico. It is found in the central, southern and northeastern portions of Arizona. Introduced and naturalized in parts of Africa and Australia.

North America & US County Distribution Map for Guilleminea densa.

U.S. Weed Information: No data available.
Invasive/Noxious Weed Information: No data available.
Wetland Indicator: No data available.
Threatened/Endangered Information: No data available.

Genus Information: 1 species in Guilleminea in the United States found in range described above. 2 varieties in Guilleminea densa, both native to Arizona;
Guilleminea densa var. aggregate, Small Matweed and
Guilleminea densa var. densa, also Small Matweed.

Comments: Small Matweed is a member of the Pigweed or Amaranth family and superficially resembles Khakiweed, Alternanthera caracasana also an Amaranth found in Arizona. Both are distinctive looking low-growing shiny green plants.

The genus was named in honor of French botanist Jean Baptiste Antoine Guillemin (1796 - 1842).

Date Profile Completed: 11/18/2014, rev. 07/19/2015, updated format 10/07/2017
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database – ITIS search
Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles as Brayulinea densa.
Steven E. Clemants, FNA | Family List | FNA Vol. 4 | Amaranthaceae | Guilleminea, FNA | Family List | FNA Vol. 4 | Amaranthaceae, FNA Vol. 4 Page 436, 437, Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford. (Accessed 11/14/2014).
Native Plant Information Network, NPIN (2013). Published on the Internet [accessed: 11/14/2014]. Lady Bird Johnson Wildflower Center at The University of Texas, Austin, TX.
1993, The Jepson Manual, Citation: ttp:// (accessed 11/14/2014)
SEINet for synonyms, scientific names and recorded geographic locations,
Wikipedia contributors, 'Guilleminea', Wikipedia, The Free Encyclopedia, 7 February 2014, 10:15 UTC, [accessed 15 November 2014]