Flora of North America species comparison

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Echinocereus rigidissimus

Echinocereus davisii

Arizona rainbow cactus, rainbow hedgehog cactus

Davis' hedgehog cactus
Habit Plants tiny, usually unbranched in the wild, nearly covered by soil (often having only 2–5 areoles exposed).
Stems

erect, spheric, (1–)2–3 × 1–2(–2.5) cm;

ribs 6–9, crests poorly defined, undulate;

areoles of largest plants 6–7(–10) mm apart.
Spines

8–14(–15) per areole, in relatively old plants curving irregularly in random directions, gray or white, some or all tipped black, dark reddish brown, or dull reddish purple;

radial spines 8–14 per areole, ± pectinately arranged, (5–)10–15(–19) mm;

central spines 0(–1) per areole, terete, 10–12 mm, closely resembling largest radial spines.
Flowers

1.5–2 × 1.5–2(–2.7) cm;

flower tube 5–8 × 5–10 mm;

flower tube hairs very short, inconspicuous;

inner tepals bright yellow-green, often with maroon midstripes, 9–18 × 2.7–3.8 mm, tips relatively thin and delicate;

anthers yellow;

nectar chamber 1 mm.
Fruits

purplish brown or remaining green when ripe, 5.5–9(–11) mm, pulp white.
2n

= 22.

Echinocereus rigidissimus

Echinocereus davisii
Phenology Flowering Feb–Mar; fruiting 1 1/2-2 months after flowering.
Habitat Semidesert grasslands, novaculite outcrops
Elevation 1200-1300 m (3900-4300 ft)
Distribution
from FNA
AZ; NM; Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
TX
[BONAP county map]
Discussion

Varieties 2 (1 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The relatively heavy, brown-and-white, often slightly contorted radial spines of Echinocereus davisii help to distinguish these tiny plants from seedlings of their larger congeners; remains of flowers and fruits, such as scattered flower tube spine-clusters, provide proof of sexual maturity. Echinocereus davisii is easily distinguished from E. viridiflorus; it is parapatric with E. viridiflorus without evidence of introgression. Echinocereus davisii is less compatible with E. viridiflorus than any varieties of E. viridiflorus are with one another (E. E. Leuck 1980).

Echinocereus davisii is in the Center for Plant Conservation’s National Collection of Endangered Plants.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 4. FNA vol. 4.
Parent taxa Cactaceae > subfam. Cactoideae > Echinocereus Cactaceae > subfam. Cactoideae > Echinocereus
Sibling taxa
E. arizonicus, E. berlandieri, E. bonkerae, E. chisosensis, E. coccineus, E. dasyacanthus, E. davisii, E. engelmannii, E. enneacanthus, E. fasciculatus, E. fendleri, E. ledingii, E. nicholii, E. papillosus, E. pectinatus, E. pentalophus, E. poselgeri, E. pseudopectinatus, E. reichenbachii, E. stramineus, E. triglochidiatus, E. viridiflorus
E. arizonicus, E. berlandieri, E. bonkerae, E. chisosensis, E. coccineus, E. dasyacanthus, E. engelmannii, E. enneacanthus, E. fasciculatus, E. fendleri, E. ledingii, E. nicholii, E. papillosus, E. pectinatus, E. pentalophus, E. poselgeri, E. pseudopectinatus, E. reichenbachii, E. rigidissimus, E. stramineus, E. triglochidiatus, E. viridiflorus
Subordinate taxa
E. rigidissimus var. rigidissimus
Synonyms Cereus pectinatus var. rigidissimus, E. pectinatus var. rigidissimus E. viridiflorus var. davisii
Name authority (Engelmann) F. Haage: Special Preisverz., 13. (1897) Houghton: Cact. Succ. J. (Los Angeles) 2: 466, fig. (1931)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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