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black-spine pricklypear, nopal violaceo, purple pricklypear

plains pricklypear

Habit Shrubs, erect to decumbent, to 1 m. Stem segments not easily detached, purple (particularly under stress) to green with purple near areoles and margins of stem segment, flattened, broadly obovate to subcircular, thickish, 7–20 × 6–18 cm; areoles 6–8(–10) per diagonal row across midstem segment, elliptic to circular, 3–7 × 2.5–5 mm; wool tan to whitish, aging black. Shrubs, low, to 0.4 m, creeping from clumps, sometimes from thickened rootstocks.
Stem

segments not easily detached, pale green to deep green, graying with age, wrinkled when stressed, flattened, broadly obovate to ovate, 6.5–15 × 4–10 cm, tuberculate, glossy, glabrous;

areoles 6–9 per diagonal row across midstem segment, oval, obovate, or subcircular, 2.5–5 × 1.5–4 mm;

wool tan, aging brown.

Spines

0 or 1–15+ per areole, few and at distal areoles or many and on most areoles, usually erect to spreading, appearing unruly, sometimes deflexed, straight or curving, acicular, often flexible, subterete to flattened basally;

longer ones reddish brown to ± black (rarely yellow to red in w Texas), or partly to wholly white, 30–120(–170) mm; reflexed spine rarely present, 1 in some areoles, short, whitish.

1–9 on most areoles to only on distal 1/2 of stem segment, white to gray with pale brown tips and bases, sometimes brown throughout;

central spines 1–3, all deflexed or 1–2 porrect or ascending, terete or flattened, occasionally spirally twisted, 25–70 mm; small spines (2–)3–6(–8) strongly deflexed, usually slender, even bristlelike, 5–15 mm.

Glochids

dense in crescent at adaxial edge of areole and well-developed subapical tuft, reddish yellow, aging brown, 2–3(–6) mm.

forming a well developed adaxial tuft, yellow to brownish white, to 6 mm.

Flowers

inner tepals yellow with red basal portions, obovate-apiculate, 25–40 mm;

filaments and anthers yellowish;

style cream;

stigma lobes green.

inner tepals yellow to gold, commonly darker to red near base, broadly spatulate, 30–40 mm, apiculate;

filaments usually pale yellow;

anthers yellow;

style whitish to pale green;

stigma lobes greenish.

Fruits

red to purplish, obovoid to barrel-shaped, 25–40 × 20–23 mm, fleshy or ± juicy, glabrous, spineless;

umbilicus 8–10 mm deep;

areoles 22–44.

purple-red, oval to broadly ovate, subspheric or short ovoid, bases not narrowed, 30 × 20–25 mm, fleshy, base not narrowed, glabrous, spineless or nearly so;

umbilicus deep;

areoles 18–30.

Seeds

yellowish, suborbicular to reniform, angled, 5–7 × 3.5–5 mm, sides flattened;

girdle protruding 0.8–1.2 mm.

whitish to tan, irregularly shaped, flattened, 4–6 × 3–4 mm;

girdle protruding 1–2 mm.

2n

= 22, 44.

= 44, 66.

Opuntia macrocentra

Opuntia tortispina

Phenology Flowering spring (Mar–Jun). Flowering spring–early summer (Apr–Jul).
Habitat Desert uplands, grasslands, oak woodlands, sandy desert flats, rocky hills and valleys Grass-lands, pinyon-juniper-oak woodlands, sandy or shaley flats, rocky hills
Elevation 900-1600 m (3000-5200 ft) 1400-1800 m (4600-5900 ft)
Distribution
from FNA
AZ; NM; TX; Mexico (Chihuahua, Coahuila, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
CO; KS; NE; NM; OK; TX; WY
[BONAP county map]
Discussion

Opuntia macrocentra var. minor is represented by relatively short and compact shrubs with a glochid pattern of a dense crescent in the adaxial edge of the areoles like the species and a much taller tuft of spreading glochids. This variety, which grows along the western side of the Rio Grande in Big Bend, Texas, appears best interpreted as a tetraploid hybrid between tetraploid putative parents, Opuntia macrocentra and O. tortispina.

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

Opuntia tortispina is apparently of hybrid origin. It has intermediate character states from its putative parents, O. macrorhiza (fleshy and spineless fruits) and O. polyacantha (areoles with basal deflexed spines and barrel-shaped fruits). The spirally twisted spines, which the specific epithet implies, are not at all characteristic for this species. When O. tortispina and O. cymochila are considered conspecific, the former has priority, as first selected by N. L. Britton and J. N. Rose (1919–1923, vol. 1).

One favored hypothesis as to the origins is that the O. humifusa-O. macrorhiza-O. pottsii complex spread across the United States from the east coast to Arizona. Opuntia polyacantha originated in north-central Mexico and spread northward. Tetraploid O. macrorhiza came into contact with the east flank of O. polyacantha and hybridized (probably repeatedly, even at present), producing the highly variable taxon referred to here as O. tortispina, which then spread eastward onto the plains. Opuntia tortispina has hexaploid members, presumably from unions of reduced and unreduced gametes. Those hexaploids apparently hybridize with hexaploid O. phaeacantha and add further to variation of O. tortispina. Many of these variations have been formally named or since treated as synonyms of O. macrorhiza.

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

Source FNA vol. 4. FNA vol. 4, p. 132.
Parent taxa Cactaceae > subfam. Opuntioideae > Opuntia Cactaceae > subfam. Opuntioideae > Opuntia
Sibling taxa
O. aciculata, O. atrispina, O. aurea, O. aureispina, O. basilaris, O. chisosensis, O. chlorotica, O. cubensis, O. ellisiana, O. engelmannii, O. ficus-indica, O. fragilis, O. humifusa, O. littoralis, 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
O. aciculata, O. atrispina, O. aurea, O. aureispina, O. basilaris, 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. triacantha, O. ×columbiana, O. ×curvispina, O. ×occidentalis, O. ×spinosibacca, O. ×vaseyi
Synonyms O. violacea, O. violacea var. castetteri, O. violacea var. macrocentra O. cymochila, O. mackensenii, O. tortispina var. cymochila
Name authority Engelmann: Proc. Amer. Acad. Arts 3: 292. (1856) Engelmann & J. M. Bigelow: Proc. Amer. Acad. Arts 3: 293. (1856)
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