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beavertail, beavertail cactus, beavertail pricklypear

Habit Shrubs, forming clumps, 1–2(–3) segments tall, to 7–40 cm.
Stem

segments not disarticulating, blue- to yellow-green, sometimes tinged maroon-purple, flattened, spatulate to broadly obovate or subcircular, thick, 5–22(–35) × 2–13.5(–16) cm, nearly smooth, papillose to puberulent (rarely glabrous);

areoles 4–16(–19) per diagonal row across midstem segment, circular to elliptic, 3–5 × 3 mm;

wool white to tan, aging gray.

Spines

0(–8) per areole, when present, usually in distal areoles, spreading, yellow, straight, acicular, 5–25 mm.

Glochids

numerous, nearly filling areoles, yellow to red-brown or dark brown, to 3 mm.

Flowers

inner tepals pink to magenta throughout (rarely white), 25–40 mm;

filaments red-magenta (rarely pale);

anthers yellowish;

style white to pink;

stigma lobes white to cream.

Fruits

maturing tan, 20–40 × 15–23 mm, dry at maturity, puberulent, spineless (except in var. treleasei);

umbilicus 5–12 mm deep;

areoles 24–76.

Seeds

yellowish to tan, ± subspheric but angular, thick, 6.5–9 × 6.5–7 mm, sides smooth or bearing 1–3 depressions;

girdle protruding to 1 mm.

Opuntia basilaris

Distribution
from FNA
AZ; CA; NV; UT; n Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 4 (4 in the flora).

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

Key
1. Stem segments bearing spines in at least several of distal areoles
var. treleasei
1. Stem segments essentially spineless (rarely 1-few per stem segment)
→ 2
2. Stem segments broadly obovoid to subcircular, erect; areoles (8-)10-16(-19) per diagonal row across midstem segment
var. basilaris
2. Stem segments spatulate to elongate, oblong, usually decumbent; areoles 4-8(-9) per diagonal row across midstem segment
→ 3
3. Stem segments spatulate, apex rounded; areoles 4-8(-9) per diagonal row across midstem segment; Arizona, Utah.
var. longiareolata
3. Stem segments oblong to narrowly spatulate to subcylindric, apex truncate to rounded; areoles 4-6(-7) per diagonal row across midstem segment; California
var. brachyclad
Source FNA vol. 4, p. 144.
Parent taxa Cactaceae > subfam. Opuntioideae > Opuntia
Sibling taxa
O. aciculata, O. atrispina, O. aurea, O. aureispina, O. chisosensis, O. chlorotica, O. cubensis, O. ellisiana, O. engelmannii, O. ficus-indica, O. fragilis, O. humifusa, O. littoralis, O. macrocentra, O. macrorhiza, O. microdasys, O. oricola, O. phaeacantha, O. pinkavae, O. polyacantha, O. pottsii, O. pusilla, O. rufida, O. santa-rita, O. stricta, O. strigil, O. tortispina, O. triacantha, O. ×columbiana, O. ×curvispina, O. ×occidentalis, O. ×spinosibacca, O. ×vaseyi
Subordinate taxa
O. basilaris var. basilaris, O. basilaris var. brachyclad, O. basilaris var. longiareolata, O. basilaris var. treleasei
Name authority Engelmann & J. M. Bigelow: Proc. Amer. Acad. Arts 3: 298. (1856)
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