Jepson eFlora
Key to families | Table of families and genera

Key to Amaranthus

View taxon page for 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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