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Amaranthus watsonii
WATSON'S AMARANTH

Higher Taxonomy
Family: AmaranthaceaeView DescriptionDichotomous Key

Common Name: AMARANTH FAMILY
Habit: Annual to subshrub; monoecious and/or dioecious; occasionally spiny; hairs simple (branched). Leaf: blade simple, alternate or opposite, margins entire or serrate; veins pinnate; stipules 0. Inflorescence: axillary or terminal; 3-flowered cymes in dense spikes, heads or panicles; bracts 0 or 1--5, persistent; bractlets 0--2. Flower: bisexual or unisexual, small, green (+- white), yellow or purple; perianth parts 0 or (1)3--5, free or fused basally, scarious or hardened, persistent; stamens 1--5, opposite perianth parts, free or basally fused as a tube, generally unequal, occasionally alternate with appendages on stamen tubes (pseudostaminodes), anthers 2- or 4-chambered; ovary superior, chamber 1; ovule 1 (2--many); style (0)1--3, stigmas 1--3(5). Fruit: utricle; generally with persistent perianth or bracts. Seed: 1 [2+], small, lenticular to spheric, smooth or dotted to striate or tubercled.
Genera In Family: +- 75 genera, 900 species: cosmopolitan, especially disturbed, arid, saline or alkaline soils; some cultivated for food, ornamental; many naturalized, ruderal or agricultural weeds. Note: Amaranthaceae including Chenopodiaceae by some. Polycnemoideae, represented in California by Nitrophila, formerly considered subfamily of Chenopodiaceae, but needs further research. Guilleminea densa (Willd.) Moq. var. aggregata Uline & W.L. Bray is a waif. Froelichia gracilis (Hook.) Moq. is an historical waif.
eFlora Treatment Author: Mihai Costea, except as noted
Scientific Editor: Douglas H. Goldman, Bruce G. Baldwin.
Genus: AmaranthusView DescriptionDichotomous Key

Common Name: AMARANTH, PIGWEED
Habit: Annual (short-lived perennial herb); monoecious or dioecious. Stem: prostrate to erect, branched or not. Leaf: alternate, petioled, ovate to linear, tip often +- notched (2-lobed), midvein ending in sharp point, margin entire, flat or wavy. Inflorescence: 3-flowered cymes, in dense axillary clusters, or large, terminal, panicle- or spike-like inflorescence; bract 1, bractlets 0--2, alike, persistent, spine-like to +- leaf-like or +- membranous, at least margins scarious-membranous. Flower: unisexual. Staminate Flower: perianth parts (2)3--5, scarious; stamens (1)2--5, filaments free; pseudostaminodes 0; anthers 4-chambered. Pistillate Flower: perianth parts (1)3--5, membranous or scarious, free, persistent; ovary ovoid, style 0, stigmas 2--3, persistent, slender, papillate; ovule 1, erect. Fruit: circumscissile or indehiscent, ovoid to obovoid, smooth or +- wrinkled, tip +- gradually (abruptly) narrowed to stigmas or beak; walls thin, membranous. Seed: 1, lenticular to +- spheric, round to obovate, smooth, shiny, occasionally obscure-dotted or -net-like, +- white-ivory to brown-red or black.
Species In Genus: +- 70 species: worldwide; weeds, ornamentals, food pls. Etymology: (Greek: unfading, non-withering) Note: Hybrids common, F1 generally with numerous, densely packed bractlets beneath generally sterile pistillate flowers, abnormal-shaped inflorescence with dense, twisted or fan-shaped branches. Unless otherwise noted, descriptions of bracts and flower parts are of pistillate flowers.
Unabridged Note: F1 hybrids have been observed in natural conditions or have been experimentally obtained between any of the following species: Amaranthus hybridus, Amaranthus powellii, Amaranthus retroflexus, Amaranthus tuberculatus, Amaranthus palmeri, Amaranthus caudatus, Amaranthus hypochondriacus, Amaranthus cruentus, Amaranthus spinosus, Amaranthus blitoides, Amaranthus albus. Amaranthus caudatus L., Amaranthus cruentus L., Amaranthus hypochondriacus L. frequently cultivated as ornamentals, occasionally escaping from cultivation. Amaranthus spinosus L. probably not naturalized, uncommon waif.

Amaranthus watsonii Standl.
NATIVE
Habit: Dioecious. Stem: erect, 10--100 cm, many-branched, green, glandular-hairy especially on bracts. Leaf: petiole 15--60 mm; blade 10--80 mm, 5--40 mm wide, ovate to obovate or oblong-elliptic, base wide-wedge shaped to +- round, tip obtuse, margins flat or +- wavy. Inflorescence: terminal with some proximal axillary clusters, erect, spike- or panicle-like, main axis generally thick, uninterrupted, 3--15 cm, 1--2 cm wide (including flowers); staminate bracts 2.2--4 mm, +- = outer perianth parts, spine-like; pistillate bracts 3--4.2 mm, 1.3--2 × > perianth, spine-like, ovate, glandular. Flower: staminate perianth parts 5, 1.5--2(3) mm, +- equal, tip acute to +- obtuse, stamens 3--5; pistillate perianth parts 5, 1.7--2.2 mm, +- equal, spoon- to fan-shaped, margin jagged, tip obtuse to +- notched, mucronate; stigmas 2--3, spreading. Fruit: circumscissile; 1.5--2 mm, < perianth, +- spheric to obovoid, +- smooth, light-brown to brown. Seed: 0.9--1.2 mm, lenticular, ovate to round, red-black, smooth, shiny.
Ecology: Coastal dunes, beaches, sandy inland areas, +- saline flats, disturbed areas after winter rain; Elevation: < 100 m. Bioregional Distribution: SnGb, s DSon (Imperial Co.); Distribution Outside California: Arizona, northwestern Mexico. Flowering Time: Aug--Sep
eFlora Treatment Author: Mihai Costea
Jepson Online Interchange
Listed on CNPS Rare Plant Inventory

Previous taxon: Amaranthus viridis
Next taxon: Guilleminea

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botanical illustration including Amaranthus watsonii

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Citation for this treatment: Mihai Costea 2016. Amaranthus watsonii, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=12955, accessed on December 10, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on December 10, 2016.


Geographic subdivisions for Amaranthus watsonii:
SnGb, s DSon (Imperial Co.);
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.