Amaranthus palmeri S. Watson, Amaranthaceae

Click on an image for links to BIGGER PICTURES

Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 11 (Go to the risk assessment).

Common name(s): [more details]

English: careless weed, dioecious amaranth, Palmer's amaranth

Habit:  herb

Description:  "Plants glabrous or nearly so. Stems erect, branched, usually (0.3-)0.5-1.5(-3) m; proximal branches often ascending. Leaves long-petiolate; blade obovate or rhombic-obovate to elliptic proximally, sometimes lanceolate distally, 1.5-7 x 1-3.5 cm, base broadly to narrowly cuneate, margins entire, plane, apex subobtuse to acute, usually with terminal mucro. Inflorescences terminal, linear spikes to panicles, usually drooping, occasionally erect, especially when young, with few axillary clusters, uninterrupted or interrupted in proximal part of plant. Bracts of pistillate flowers with long-excurrent midrib, 4-6 mm, longer than tepals, apex acuminate or mucronulate; of staminate flowers, 4 mm, equaling or longer than outer tepals, apex long-acuminate. Pistillate flowers: tepals 1.7-3.8 mm, apex acuminate, mucronulate; style branches spreading; stigmas 2(-3). Staminate flowers: tepals 5, unequal, 2-4 mm, apex acute; inner tepals with prominent midrib excurrent as rigid spine, apex long-acuminate or mucronulate; stamens 5. Utricles tan to brown, occasionally reddish brown, obovoid to subglobose, 1.5-2 mm, shorter than tepals, at maturity walls thin, almost smooth or indistinctly rugose. Seeds dark reddish brown to brown, 1-1.2 mm diameter, shiny"  (Flora of North America online).

Habitat/ecology:  "Streambanks, disturbed habitats, especially agricultural fields, railroads, waste areas, roadsides; 100-1000 m"  (Flora of North America online).

Propagation:  Seed

Native range:  United States and Mexico (GRIN).

Presence:

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Canada Canada	Canada (country)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 182)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	native	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Additional information:
Additional online information about Amaranthus palmeri is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Amaranthus palmeri as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Amaranthus palmeri may be available from the Germplasm Resources Information Network (GRIN).

References:

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.