The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

hair-spine prickly pear, panhandle prickly pear, plains prickly pear, starvation prickly-pear

black-spine pricklypear, nopal violaceo, purple pricklypear

Habit Shrubs, low, 10–25 cm, with ± prostrate branches. 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.
Stem

segments not easily detached, green, elliptic to narrowly to broadly obovate to circular, 4–27 × 2–18 cm, low tuberculate;

areoles 4–14 per diagonal row across midstem segment, subcircular, 3–6 mm;

wool tan to brown.

Spines

at all or only distal areoles of stem segment, terete to flattened, stout to acicular to bristlelike, straight to curling, of 1 or 2 kinds;

if 1 kind: 0–18 per areole, spreading and curling in various directions, sometimes straight, erect, ascending to deflexed, yellow to dark brown to black, turning gray, pink-gray to gray-brown, longest (35–)40–90(–185) mm;

if ± 2 kinds: major spines (0–)1–5, reflexed to porrect, yellow-brown to brown to gray, longest 20–150 mm;

minor spines (0–)5–11, deflexed, white to white-gray, longest 4–16 mm.

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.

Glochids

inconspicuous, in narrow, tidy crescent at adaxial edge of areole or in broad, brushy crescent and tuft, yellow to reddish, aging brown, to 10 mm.

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

Flowers

inner tepals yellow to magenta throughout, 25–40 mm;

filaments white, yellow, or red to magenta (flowers may superficially appear bicolored);

anthers yellow;

style white to pale pink;

stigma lobes green.

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

filaments and anthers yellowish;

style cream;

stigma lobes green.

Fruits

tan to brown, ± cylindric, 15–45 × 12–25 mm, dry at maturity, glabrous, sometimes burlike;

areoles 10–33, each or only distal areoles bearing 3–16 spines, 4–20 mm.

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.

Seeds

tan to gray, flattened, warped, oblong to subcircular, 3–7 × 2–4 mm;

girdle protruding 1–2 mm.

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

girdle protruding 0.8–1.2 mm.

2n

= 22, 44.

Opuntia polyacantha

Opuntia macrocentra

Phenology Flowering spring (Mar–Jun).
Habitat Desert uplands, grasslands, oak woodlands, sandy desert flats, rocky hills and valleys
Elevation 900-1600 m (3000-5200 ft)
Distribution
from FNA
AZ; CA; CO; ID; KS; MT; ND; NE; NM; NV; OK; SD; TX; UT; WY; AB; SK; n Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; NM; TX; Mexico (Chihuahua, Coahuila, Sonora)
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 5 (5 in the flora).

Populations of Opuntia polyacantha with spines few or absent (especially var. hystricina) were the basis for several names including O. juniperina, O. utahensis, and O. rhodantha.

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

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.)

Key
1. Areoles 4-6 per diagonal row across midstem segment; stem segments 4-7 × 2-3(-5) cm, elliptic to very narrowly obovate; Texas, New Mexico, Mexico
var. arenaria
1. Areoles 6-14 per diagonal row across midstem segment; stem segments 6-27 × 5-18 cm, obovate to circular or, if elliptic, longer than 9 cm; widespread in w United States and Canada
→ 2
2. Spines of 2 kinds: major spines 1-3 per areole, usually deflexed on terminal stem segment, but sometimes ascending at stem segment apex; minor spines 1-3 per areole, deflexed, white, subtending major spines
→ 3
2. Spines of 1 kind, grading in length, from ascending to deflexed, 7-18 per areole, longest spines of terminal stem segment porrect to ascending, shorter spines deflexed to porrect
→ 4
3. Longest spines 2-4 cm; areoles 6-13 mm apart; stem segments 6-12 cm; Great Plains, n and e Great Basin Desert
var. polyacantha
3. Longest spines 4.5-12 cm; areoles 12-30 mm apart; stem segments 10-27 cm; Arizona and Utah border
var. nicholii
4. Spines usually dark brown, those of proximal stem segments like those of terminal stem segments, porrect to ascending, straight and stiff; fruit areoles 11-21, spiny but not burlike
var. hystricina
4. Spines usually pale, those of proximal stem segments not like those of terminals stem segments, more numerous, longer and more reflexed, straight or flexuous and/or hairlike or threadlike; fruit areoles 20-33, spiny, forming dense bur
var. erinacea
Source FNA vol. 4. FNA vol. 4.
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. macrocentra, O. macrorhiza, O. microdasys, O. oricola, O. phaeacantha, O. pinkavae, 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. 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. polyacantha var. arenaria, O. polyacantha var. erinacea, O. polyacantha var. hystricina, O. polyacantha var. nicholii, O. polyacantha var. polyacantha
Synonyms Cactus ferox, Tunas polyacantha O. violacea, O. violacea var. castetteri, O. violacea var. macrocentra
Name authority Haworth: Suppl. Pl. Succ., 82. (1819) Engelmann: Proc. Amer. Acad. Arts 3: 292. (1856)
Web links