Opuntia basilaris

Engelmann & J. M. Bigelow

Proc. Amer. Acad. Arts 3: 298. 1856.

Common names: Beavertail pricklypear
Treatment appears in FNA Volume 4. Treatment on page 144. Mentioned on page 143.

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.


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Ariz., Calif., Nev., Utah, n Mexico.


Varieties 4 (4 in the flora).

Selected References



1 Stem segments bearing spines in at least several of distal areoles Opuntia basilaris 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 Opuntia basilaris 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. Opuntia basilaris 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 Opuntia basilaris var. brachyclad