Opuntia macrorhiza

Engelmann

Boston J. Nat. Hist. 6: 206. 1850.

Common names: Western pricklypear
Illustrated
Synonyms: Opuntia compressa var. macrorhiza (Engelmann) L. D. Benson Opuntia mesacantha var. acrorhiza (Engelmann) J. M. Coulter
Treatment appears in FNA Volume 4. Mentioned on page 131.

Shrubs, forming clumps, 7.5–16 cm, sometimes from tuberlike rootstocks. Stem segments not easily detached, dark dull green, often cross wrinkled when stressed, flattened, obovate to circular, 5–11 × 3.5–7.5 cm, fleshy (to flabby and cross wrinkled when stressed), tuberculate, glaucous; areoles 5–6 (–8) per diagonal row across midstem segment, oval to subcircular, 2–4 mm diam.; wool tan. Spines (0–) 1–4 per areole, usually in distal areoles, erect to spreading, white to redbrown, acicular, straight, terete or 1 flattened, ± stout (0.5 mm diam. at base), longest to 60 mm. Glochids in dense tuft, pale-yellow, tan to redbrown, aging brown, to 5 mm. Flowers: inner tepals yellow with red basal portions, 25–40 mm; filaments pale-yellow; anthers yellow; style white; stigma lobes cream to yellowish. Fruits green to yellowish to dull red, stipitate, elongate-obovoid, 25–40 × 15–28 mm, fleshy, glabrous; areoles 16–28. Seeds tan, subcircular, 4–5 mm, thickish, warped; girdle broad, protruding to 0.5 mm. 2n = 44.


Phenology: Flowering late spring (May–Jun).
Habitat: Plains, chaparral, grassy woodlands, coniferous forests, sandy to loamy soils
Elevation: 100-2300 m

Distribution

V4 245-distribution-map.gif

Ariz., Ark., Colo., Kans., Mo., N.Mex., Okla., Tex., Utah, Mexico (Chihuahua)

Discussion

Opuntia macrorhiza hybridizes with the hexaploid O. engelmannii (apparently var. lindheimeri) forming the pentaploid O. ×edwardsii V. E. Grant & K. A. Grant. This hybrid is a small subshrub, 20–40 cm, with a mixture of widely spaced, unequal glochids and closely spaced, shorter glochids. Its major spines are gray, and its tepals are yellow or yellow with red bases. Those characteristics are similar to one parent or the intermediate of the two putative parents reported from Blanco and Guadalupe counties, central Texas.

Selected References

None.

Lower Taxa

None.

"thickish" is not a number.

... more about "Opuntia macrorhiza"
cushionlike +
0.8 cm8 mm <br />0.008 m <br /> (1 cm10 mm <br />0.01 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (1 cm10 mm <br />0.01 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
deciduous +  and persistent +
0.3 cm3 mm <br />0.003 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
16 +  and 28 +
oval +  and subcircular +
0.1 cm1 mm <br />0.001 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Donald J. Pinkava +
Engelmann +
proliferating +
flattened +  and cylindric +
Western pricklypear +
Ariz. +, Ark. +, Colo. +, Kans. +, Mo. +, N.Mex. +, Okla. +, Tex. +, Utah +  and Mexico (Chihuahua) +
100-2300 m +
15 cm150 mm <br />0.15 m <br /> (30 cm300 mm <br />0.3 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (15 cm150 mm <br />0.15 m <br />) +
burlike +  and spiny +
green;yellowish +
straight +
indehiscent +
persistent +, long +  and deciduous +
25mm;40mm +
proliferating +
tuberculate +  and smooth +
elongate-obovoid +
1.5 cm15 mm <br />0.015 m <br /> (2.8 cm28 mm <br />0.028 m <br />) +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
0 cm0 mm <br />0 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
foveolate +  and reticulate +
Plains, chaparral, grassy woodlands, coniferous forests, sandy to loamy soils +
oblong +  and spatulate +
2.5 cm25 mm <br />0.025 m <br /> (4 cm40 mm <br />0.04 m <br />) +
deciduous +
flattened +  and conic +
0 cm0 mm <br />0 m <br /> (3 cm30 mm <br />0.03 m <br />) +
succulent +
tuberculate +
fluted;spheric;depressed-spheric or club-shaped +
tinged color +
open +  and simple +
sometimes covered by outgrowths of proximal portion of style base or of flower tube wall +  and open +
persistent +  and deciduous +
Flowering late spring (May–Jun). +
ridgelike +  and nipple--shaped +
Boston J. Nat. Hist. +
3;2;2;30 +
tuberlike +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
warped;subcircular +
Illustrated +
not sheathed +
7.5 cm75 mm <br />0.075 m <br /> (17 cm170 mm <br />0.17 m <br />) +
white +  and redbrown +
straight +
deciduous +  and persistent +
erect +  and spreading +
conspicuous +
with hairlike bristles +  and setose +
1 (?) +  and 4 (?) +
flattened +, terete +  and acicular +
0 cm0 mm <br />0 m <br /> (6 cm60 mm <br />0.06 m <br />) +
hard +  and rigid +
decurrent +
winged +  and unsegmented +
tuberculate +  and smooth +
60 cm600 mm <br />0.6 m <br /> (120 cm1,200 mm <br />1.2 m <br />) +
green +  and dark +
5 cm50 mm <br />0.05 m <br /> (11 cm110 mm <br />0.11 m <br />) +
tuberculate +  and wrinkled +
3.5 cm35 mm <br />0.035 m <br /> (7.5 cm75 mm <br />0.075 m <br />) +
segmented +
woody +  and succulent +
cream +  and yellowish +
Opuntia compressa var. macrorhiza +  and Opuntia mesacantha var. acrorhiza +
adventitious +
tuberlike +
epipetric +  and epiphytic +
Opuntia macrorhiza +
species +
dull +  and glossy +
yellow +  and paler +
segmented +
terrestrial;epiphytic or epipetric +
erect +  and trailing +