Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

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

Cirsium ochrocentrum, Yellowspine Thistle

Alternanthera pungens, Khakiweed

Khakiweed flowers are white and nestled within straw colored bracts. You may note that the flowers are axillary and emerge from nodes along the stems. The seeds are ovate and the fruit is a one-seeded utricle. Alternanthera pungens Khakiweed plants form dense mats. They are a creeping, prostrate to procumbent plant that spreads by seed and vegetatively as roots develop from nodes at the spreading stem, the fleshy taproot keeps plants alive during periods of drought. Alternanthera pungens Khakiweed plants have villous (shaggy with soft hairs) and glabrescent (becoming hairless, or smooth) stems, leaves are elliptical to obovate with pilose (soft, thin, clearly separated hairs) and glabrescent surfaces. Contrary to publish literature as you can see in the photograph, the leaves are not always sessile (without a stalk). Alternanthera pungensKhakiweed is a perennial species found at elevations from sea level to 5,000 feet; it is native to Central and South America but is now widely established in Australia and Southern Africa. Plants bloom from May and June perhaps well into the summer. Alternanthera pungensKhakiweed specimens on this page were observed in a south Scottsdale public park growing in bare places and in Bermuda grass. At this time I do not believe this species is recognized as occurring in central Arizona and possibly in Arizona. This species was long known as Alternative repens and is suspected to have poisoned pigs and cattle that consumed it. Alternanthera pungens

Scientific Name: Alternanthera pungens
Common Name: Khakiweed
Also Called: Alligatorweed, Creeping Chaffweed, Khaki-Weed
Family: Amaranthaceae, Pigweed Family
Synonyms: (Achyranthes leiantha, Achyranthes mucronata, Achyranthes radicans, Achyranthes repens, Alternanthera achyrantha, Alternanthera repens)
Status: Introduced - Central and South America, now widely established in Australia and Southern Africa.
Duration: Perennial
Size: 1 to 2.5 feet.
Growth Form: Forb/herb; forms dense mats; a creeping, prostrate to procumbent plant, stems villous, glabrescent; spreads by seed and vegetatively as roots develop from nodes at the spreading stem, the fleshy taproot keeps plants alive during periods of drought.
Leaves: Green; not always sessile, leaves elliptical to obovate; leaf surfaces pilose, glabrescent.
Flower Color: White with straw bracts; stramineous) or whitish; flowers axillary, flowers are lanceolate tepals; seeds ovate; fruit are stemless, prickly, papery, fruit is a one seeded utricle, stemless, khaki in color.
Flowering Season: Summer through fall. (May and June observed)

Elevation: Sea level to 5,000 feet.

Habitat Preferences: Lawns, waste grounds and limestone areas

Recorded Range: Khakiweed is an introduced species reported in AL, AZ, GA, LA, NY, SC, TX and VA. Herbarium records from SEINet report the species in SE AZ (Pima, Cochise, and Santa Cruz counties) are possibly that of Alternanthera repens (A. caracasana). It is native to South America.

North America & US County Distribution Map for Alternanthera pungens.

U.S. Weed Information: In North America Alternanthera pungens can be weedy or invasive according to the following authoritative sources: Weeds of the West, Western Society of Weed Science in cooperation with Cooperative Extension Services, University of Wyoming. Laramie, Wyoming. Plants included here may become weedy or invasive.

Invasive/Noxious Weed Information: In North America the genus Alternanthera is listed as a Noxious Weed by the State of Arkansas. Plants included here are invasive or noxious.

Wetland Indicator: Unknown
Threatened/Endangered Information: Unknown

Genus Information: In North America there are 15 species and 17 accepted taxa overall for Alternanthera; mostly in the southern parts of the United States and Mexico. 9 species introduced, 4 native. 2 introduced species in Arizona. Worldwide, The Plant List includes 137 accepted species names and a further 164 scientific names of infraspecific rank for Alternanthera.

In the Southwestern United States: Texas has 3 native species. All data is approximate and subject to taxonomic changes.

Comments: Khaki Weed is an introduced species from Central and South America. It is now widely established in Australia and Southern Africa.

The specimens above were observed in a south Scottsdale public park growing in bare places and in Bermuda grass. At this time I do not believe this species is recognized as occurring in central Arizona and possibly in Arizona. In the states of record in which this species occurs, the USDA Plants Database does not include Arizona. However, the Flora of North America states that records indicate specimens of this species have been identified in the Herbarium at Arizona State University, Tempe, Arizona. If so, the specimens are possibly that of A. repens (=A. caracasana).

Alternanthera pungens was long known as Alternative repens and is suspected to have poisoned pigs and cattle that consumed it.

In Southwest Desert Flora also see a closely related species also called "Khaki Weed", Alternathera caracasana.

Khaki Weed is similar in appearance and habitat to another member of the Amaranth family, Small Matweed, Guilleminea densa, also an Amaranth found in Arizona.

Etymology:

The genus "Alternanthera" comes from the Latin alternus, "alternate", and the Greek anthera "anther", referring to the stamens and anthers which are alternately fertile and barren (sterile). The species epithet "pungens" means both "sharply pointed" and "pricking, puncturing or stinging" referencing the flowers and fruits.

Ethnobotany

No information available
Date Profile Completed: 05/30/2019
References:
Kearney, Thomas H., Peebles, Robert H., 1960, Arizona Flora, University of California Press, Berkley and Los Angeles, California.
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 05/27/2019).
Wunderlin, R. P., B. F. Hansen, A. R. Franck, and F. B. Essig. 2019. Atlas of Florida Plants (http://florida.plantatlas.usf.edu/). [S. M. Landry and K. N. Campbell (application development), USF Water Institute.] Institute for Systematic Botany, University of South Florida, Tampa. (accessed 05/27/2019).
The Plant List (2013). Version 1.1. Published on the Internet; http://www.theplantlist.org/tpl1.1/record/kew-2631391 (accessed 05/27/2019).
Steven E. Clemants, FNA | Family List | FNA Vol. 4 | Amaranthaceae | Alternanthera, Pages 448, 450; Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford, (accessed 05/27/2019).
SEINet synonyms, scientific names, geographic locations, general information, (accessed 05/27/2019).
http://swbiodiversity.org/seinet/
Champion, Paul & Hofstra, Deborah Hofstra (NIWA): New Zealand Plant Conservation Network: National Institute of Water and Atmospheric Research (NIWA)
Wikipedia contributors, 'Alternanthera', Wikipedia, The Free Encyclopedia, 21 May 2019, 01:27 UTC, https://en.wikipedia.org/w/index.php?title=Alternanthera&oldid=898047862 [accessed 28 May 2019]
Wikipedia contributors, 'Alternanthera pungens', Wikipedia, The Free Encyclopedia, 13 October 2018, 22:44 UTC, https://en.wikipedia.org/w/index.php?title=Alternanthera_pungens&oldid=863915626 [accessed 29 May 2019]
Keener, B. R., A.R. Diamond, L. J. Davenport, P. G. Davison, S. L. Ginzbarg, C. J. Hansen, C. S. Major, D. D. Spaulding, J. K. Triplett, and M. Woods. 2019. Alabama Plant Atlas. [S.M. Landry and K.N. Campbell (original application development), Florida Center for Community Design and Research. University of South Florida]. University of West Alabama, Livingston, Alabama.