Jepson eFlora
Key to families | Table of families and genera

Key to Opuntia

View taxon page for Opuntia

1. Stem generally velvety to minutely papillate-hairy (puberulent), or if glabrous then perianth pink-magenta, stigma white, seeds ± spheric

2. Tree < 6 m, trunks > 15 cm diam — sexually mature when young and ± shrubby ..... [O. leucotricha]

2' Shrub generally < 1 m, all or most branches ± touching the ground

3. Perianth yellow, stigma green; seed 2–3 mm ..... O. microdasys

3' Perianth pink-magenta, stigma white; seed 6.5–9 mm ..... O. basilaris

4. Spines 2–8, rigid, < 2.6 cm — c Kern Co. ..... var. treleasei

4' Spines 0, barbed bristles present

5. Stem segment length < 2 × width, width > 5 × thickness ..... var. basilaris

5' Stem segment length > 2 × width, width < 2 × thickness ..... var. brachyclada

1' Stem glabrous; if perianth pink-magenta then stigma green and seeds ± flat-sided

6. Terminal stem segment generally easily detached when fresh, 2–5.5 cm, width ± = thickness; w High Cascade Range (Siskiyou Co.) ..... O. fragilis

6' Terminal stem segments firmly attached when fresh, > 4 cm, width > 4 × thickness; mostly Southwestern California, D

7. Fruit dry in age, tan, generally spiny; perianth yellow to pink-magenta; style slender, white, base ± thicker ..... O. polyacantha

8. Spines generally pale, more numerous and hair-like, curling, reflexed near plant base; ovary areoles 20–33; fruit generally a densely spiny bur ..... var. erinacea

8' Spines generally brown to black, spreading to ascending, straight, stiff on all stem segments; ovary areoles 11–21; fruit less spiny, not bur-like ..... var. hystricina

7' Fruit juicy, generally with some deep purple, spines 0; perianth yellow, orange, or red; style thick, white to red, base much thicker

9. Trunk 1, erect; areoles generally > 38 per ovary

10. Mature plant > 3 m; stem bristles < 1 mm, inconspicuous; ovary tubercled when fresh ..... O. ficus-indica

10' Mature plant < 2.5 m; stem bristles 2–12 mm, conspicuous; ovary smooth

11. Longest spines generally 25–50 mm; style white when fresh; seed 3 mm; e Peninsular Ranges, Mojave Desert (desert mountains and lower montane slopes, canyons) ..... O. chlorotica

11' Longest spines 19–25(50) mm; style red when fresh; seed 3.5–4 mm; Southwestern California ..... O. oricola

9' Basal branches several, ± decumbent to ascending; areoles <= 36 per ovary

12. Style and filaments white

13. Stem segment < 14 cm wide; perianth base red; fruit generally green inside ..... O. phaeacantha

13' Stem segment > 15 cm wide; perianth base yellow; fruit red inside

14. Stem segment lightly glaucous, gray-green, generally obovate, < 20 cm wide ..... O. engelmannii var. engelmannii

14' Stem segment strongly glaucous, ± silvery-blue, round, > 25 cm wide ..... [O. robusta]

12' Style pink or filaments yellow to orange-yellow (or both)

15. Stem segment > 15 cm wide ..... O. ×occidentalis

15' Stem segment < 15 cm wide

16. Stem segment oblong-elliptic to narrowly obovate; major spines generally round, 4–11 per areole ..... O. littoralis

16' Stem segment generally obovate; major spines generally flat, generally 0–4 per areole ..... O. ×vaseyi

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