Jepson eFlora
Key to families | Table of families and genera

Key to Opuntia

View taxon page for Opuntia

(For a list of species in Opuntia, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

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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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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