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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.


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.
± 70 species: worldwide; weeds, ornamentals, food plants. (Greek: unfading, non-withering) [Costea et al. 2001 Sida 19:931–974, 975–992; Sauer 1967 Ann Missouri Bot Gard 54:103–137] 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 references: [Sauer 1955 Madroño 13:5–46]
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.

Key to Amaranthus

1. Dioecious

2. Plant in hand pistillate

3. Perianth parts 1–2, 1 narrowly lanceolate, 1 rudimentary or 0 ..... A. tuberculatus var. rudis (2)

3' Perianth parts 5, well developed, fan- or spoon-shaped

4. Bracts <= perianth parts ..... A. arenicola (2)

4' Bracts > than perianth parts

5. Plant ± glabrous; outer perianth parts ± acuminate ..... A. palmeri (2)

5' Plant glandular-hairy especially on bracts; outer perianth parts obtuse to ± notched, mucronate ..... A. watsonii (2)

2' Plant in hand staminate

6. Bracts <= 2 mm ..... A. tuberculatus var. rudis (2)

6' Bracts (1.4)2–6 mm

7. Outer perianth parts acuminate, spine-tipped; bracts >= perianth parts ..... A. palmeri (2)

7' Outer perianth parts mucronate; bracts <= perianth parts

8. Inflorescence axis and bracts glabrous ..... A. arenicola (2)

8' Inflorescence axis and bracts generally sparsely glandular-hairy ..... A. watsonii (2)

1' Monoecious

9. Nodes with 2 spines ..... [A. spinosus]

9' Nodes without spines

10. Perianth parts 1–3, only 1 well developed ..... A. californicus

10' Perianth parts (2)3–5, all well developed.

11. Pistillate perianth parts fan-shaped, margins fringed or finely dentate ..... A. fimbriatus

11' Pistillate perianth parts not fan-shaped, margins entire

12. Inflorescence of axillary clusters only, or axillary and terminal

13. Perianth parts (3)4–5

14. Perianth parts narrow-ovate to oblong; seeds 1.3–1.7 mm ..... A. blitoides

14' Perianth parts narrow-spoon-shaped; seeds 0.9–1.1 mm ..... A. torreyi

13' Perianth parts (2)3

15. Fruit dehiscent; bracts 1.5–4 mm, tip ± spined ..... A. albus

15' Fruit indehiscent; bracts <= 1 mm, tip not spined

16. Stem hairy distally; fruit 2–3 mm, smooth ..... A. deflexus

16' Stem ± glabrous; fruit 1.2–1.5 mm, wrinkled

17. Leaf tip entire or ± notched; seeds dull, dotted ..... [A. viridis]

17' Leaf tip deeply notched to 2-lobed; seeds shiny, only margins dotted ..... [A. blitum subsp. emarginatus]

12' Inflorescence terminal only

18. Inflorescence green; bracts > stigma; seeds brown to black; often weedy

19. Perianth parts spoon-shaped to obovate, overlapping, reflexed in age, tip rounded to ± notched ..... A. retroflexus

19' Perianth parts linear to lance-oblong, not overlapping, erect, tip acute to awned

20. Leaf blades rhombic-ovate or widely lanceolate; inflorescence of many thin, flexible branches; bracts 2–4 mm ..... A. hybridus

20' Leaf blades elliptic, rhombic to widely lanceolate; inflorescence of few rigid, erect branches; bracts 4.5–6(8) mm ..... A. powellii

18' Inflorescence brightly colored, not green; bracts generally <= stigma; seeds white to ± red-brown or black; cultivated, rarely escaped

21. Inflorescence main axis generally drooping or nodding; perianth parts widely spoon-shaped, margins overlapping, tip obtuse to rounded ..... [A. caudatus]

21' Inflorescence not drooping or nodding; perianth parts linear to elliptic (obovate), margins not overlapping, acute to acuminate (rounded)

22. Inflorescence erect to flexible, lateral axes thin, flexible, 3–8(12) cm, 0.5–1 cm wide; bracts 1.8–2.5 mm; fruit tip abruptly narrowed to a beak ..... [A. cruentus]

22' Inflorescence erect, lateral axes thick, stiff, 9–20(30) cm, 1.2–2 cm wide; bracts 3–5(6) mm; fruit tip gradually narrowed ..... [A. hypochondriacus]


Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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