Fringed Amaranth

Two varieties of Amaranthus fimbriatus have been recognized: var. fimbriatus, with tepals fimbriate at the apex, and var. denticulatus (= A. venulosus S. Watson), with denticulate or crenulate tepals. The latter is reported from Arizona and adjacent northern Mexico; it probably occurs more widely.

A related species, Amaranthus chihuahuensis S. Watson, which occurs in Mexico (Chihuahua and Oaxaca), was reported from trans-Pecos Texas, but no reliable specimens were seen by C. F. Reed (1969b). The presence of that species in the United States needs confirmation, and its taxonomic identity remains obscure.

Plants glabrous. Stems erect or with lateral branches ascending, usually branched from base, main and lateral stems sparingly branched or simple, 0.3-0.7(-1) m. Leaves short-petiolate; petiole ¹/4-¹/2 as long as blade; blade linear to narrowly lanceolate, (1-)2-6(-10) × 0.1-0.5(-1) cm, base narrowly cuneate, margins entire, plane, apex acute to mucronulate. Inflorescences mostly axillary clusters scattered from base to apex of plants, distally condensed in lax, unbranched, almost leafless, slender, terminal spikes, interrupted. Bracts of pistillate flowers ovate to ovate-lanceolate, 1-1.8 mm, shorter than tepals, about ¹/2 or less as long as tepals. Pistillate flowers: tepals 5, reflexed, fan-shaped to broadly spatulate, clawed, equal or subequal, 1.5-3.3 mm, margins fimbriate or denticulate, apex much expanded and obtuse; style branches erect to ± spreading; stigmas 3(-4). Staminate flowers: tepals 5, apex obtuse; stamens (2-)3. Utricles subglobose to obovate, 1.2-2 mm, shorter than tepals, rugose to nearly smooth, dehiscence regularly circumscissile. Seeds black or dark reddish brown, lenticular to broadly lenticular, 0.8-1 mm diam., shiny, smooth. 2n = 34.

Ariz., Calif., N.Mex., Tex., Utah; n Mexico.

Flowering summer-fall (in arid regions mostly after summer rains).

Sandy, gravelly slopes, washes, semideserts, disturbed habitats; 500-1700m.

Sarratia berlandieri Moquin-Tandon var. fimbriata Torrey in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 179. 1859; Amaranthus fimbriatus var. denticulatus (Torrey) Uline & W. L. Bray

Amaranthus fimbriatus is a species of glabrous flowering plant in the Amaranthaceae family. It is commonly known as fringed amaranth or fringed pigweed. The plant is an annual herb that can often grow up to 0.7 m (2 ft.) in height. The flower is greenish to maroon. It is found in North America and in Mexico. It often grows on sandy, gravelly slopes, semideserts or in disturbed habitats. It usually blooms after the summer rains in these arid regions. It is considered to be an invasive weed.

Two varieties of A. fimbriatus have been described: A. fimbriatus var. fimbriatus and A. fimbriatus var. denticulatus. The small variations are found in the tepals.