This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Several florae provide keys for identifying brittle pricklypear [9,32,45,50,80].
Brittle pricklypear is a perennial native mat- or clump-forming cactus, usually 2 to 4 inches (5-10 cm) tall. The clumps or mats often exceed 12 inches (30 cm) in diameter. The succulent stem segments, or pads, are 0.5 to 5 inches (1.2-2.5 cm) wide and range in length from 0.8 to 2 inches (2-5 cm) for pygmy pricklypear and 2 to 2.8 inches (5-7cm) for little pricklypear. Aereoles on the pads give rise to 2 to 7 barbed spines that are 0.5 to 0.8 inch (1.2-2 cm) long for pygmy pricklypear and 0.8 to 1.2 inches (2-3) cm long for little pricklypear. Flowers are solitary, 1.2 to 2 inches (3-5 cm) long and broad. The fruit is a pear-shaped berry, 0.6 to 0.8 inch (1.5-2 cm) long, and is usually spiny. The seeds are glabrous, flattened, oblong to subcircular, and 0.2 inch (5 mm) in diameter. The root system is shallow and fibrous [9,21,50,68].
Brittle pricklypear is extremely tolerant of drought. It avoids drought damage by accumulating water in storage cells that contain mucilaginous materials with a strong water-retaining capacity [37].
Brittle pricklypear is widely distributed across North America. It occurs from Ontario south to Texas and west to British Columbia, Washington, Oregon, and California. Brittle pricklypear is rare in Ontario, Iowa, Illinois, Michigan, Washington, and Wisconsin [39,77], and extremely rare or possibly extirpated in California [17,39]. Brittle pricklypear is found further north than any other cactus species in the world, growing in northern Alberta only 4o south of the Arctic Circle [9]. The Flora of North America provides a distribution map of brittle pricklypear. Plants database provides state distributional maps of its varieties.
Varieties: Pygmy pricklypear occurs throughout the general range of brittle pricklypear. Little pricklypear occurs in Colorado, New Mexico, Arizona, and Utah [39].
Brittle pricklypear can flourish on a great range of sites. It is found at elevations ranging from sea level to 11,089 feet (3,380 m), will grow well on various types of soils under a wide range of moisture regimes, and can survive extremes of both hot and cold temperatures [9,48,80].
Brittle pricklypear is perhaps the most cold tolerant of all the cacti species, being able to survive on sites where the minimum winter temperatures can drop below -58 oF (-50 oC). The cactus avoids freeze damage by rapidly reducing the water content in cells during cold acclimation. The short stature of the plants allows brittle pricklypear to take advantage of the insulating effects of snow and the thermal environment at the soil surface. Brittle pricklypear also is able to withstand temperatures in excess of 131 oF (55 oC) [37,48].
Brittle pricklypear is most commonly found on rocky, sandy or gravely soils, but can also flourish on silty, loamy, or clayey soils. It is tolerant of salt-affected, alkaline, and solodized (dealkalized) soils [9,80,81].
The moisture regimes at which brittle pricklypear can be found are quite varied. For example, in British Columbia, brittle pricklypear occurs on sites ranging from very xeric to hygric [42].
The following table lists reported elevational ranges for brittle pricklypear:
State or province Elevation AZ 6,500 to 7,500 feet (1,981-2,286 m) [40] CO 4,500 to 7,500 feet (1,372-2,286 m) [28] NM 4,500 to 8,000 feet (1,372-2,438 m) [50] UT 4,495 to 8,415 feet (1,370-2,565 m) [80] WA 14 to 4,500 feet (4-1,372 m) [77] BC 738 to 11,089 feet (225-3,380) [42]Stems, fruits, and seeds of brittle pricklypear may comprise an appreciable portion of the diet of at least 44 species of birds and mammals [8]. For example, a study near Flagstaff, Arizona, showed that brittle pricklypear and twist-spine pricklypear (Opuntia macrorhiza) were major food items for Botta's pocket gophers in winter and spring. Although use was less, the pocket gophers also consistently grazed pricklypears in summer and fall [7]. The pads of Opuntia species can be used as emergency forage for livestock after the spines have been singed off [34].
Brittle pricklypear provides food for cactus-feeding insects including moths, bugs, and beetles. For a list of insect species that graze brittle pricklypear, see [8,15,76].
Palatability/nutritional value: Brittle pricklypear is low in nutritional value for livestock [34].
Cover value: No information is available on this topic.
Brittle pricklypear occurs in a variety of desert, grassland, prairie, and
woodland communities. It occurs as a community associate and not a dominant
species [9]. Brief descriptions of the common dominants and associates
are presented below. More detailed descriptions of plant communities where brittle
pricklypear occurs are available in the publications listed at the end of this
section.
Brittle pricklypear is commonly found in upland grasslands dominated
by various bunchgrasses including blue grama (Bouteloua gracilis),
buffalo grass (Buchloe dactyloides), Sandberg bluegrass (Poa
secunda), bluebunch wheatgrass (Pseudoroegneria spicata), western wheatgrass (Pascopyrum smithii),
and green needlegrass (Nassella viridula) [31,46,55,72,81].
In tallgrass prairies dominated by big bluestem (Andropogon gerardii)
and little bluestem (Schizachyrium scoparium), brittle pricklypear
occurs but is an uncommon associate [30,81].
Brittle pricklypear is a common associate in a wide variety of habitat
types dominated by big sagebrush (Artemisia tridentata) and silver
sagebrush (A. cana). It also occurs as an associate in various
shrub communities including those dominated by greasewood (Sarcobatus
vermiculatus), shadscale saltbush (Atriplex confertifolia), and
blackbrush (Coleogyne ramosissima) [14,31,49,72].
In the Sandhills region of Colorado and Nebraska, brittle pricklypear is commonly
found in communities dominated by sand sagebrush (Artemisia
filifolia), prairie sandreed (Calamovilfa longifolia), sand
bluestem (Andropogon gerardii var. paucipilus), hairy grama (Bouteloua
hirsuta), and sandhill muhly (Muhlenbergia pungens) [58,62].
Brittle pricklypear occurs in various woodland communities, notably dry ponderosa pine
(Pinus ponderosa) communities,
dry ponderosa pine-Douglas-fir (Pseudotsuga menziesii) habitat types, pinyon-juniper (P.
edulis-Juniperus spp.) woodlands and Gambel oak (Quercus
gambelii) thickets [1,51,77,79,80].
Publications that discuss plant communities in which brittle pricklypear
occurs are listed below. The list is neither restrictive nor all
inclusive.
Brittle pricklypear flowers from May at low elevations to July at high elevations. Fruits mature 2 to 3 months after flowering and many persist until the following spring [9,25,50]. FIRE ECOLOGY SPECIES: Opuntia fragilis
FIRE ECOLOGY OR ADAPTATIONS:FIRE REGIMES: Brittle pricklypear occurs in plant communities with a wide range of fire frequencies, from less than 10 years for many prairie and grassland communities, to the 400 years possible for the Colorado pinyon (Pinus edulis) community. As of this writing (2005), fire ecology studies are lacking for brittle pricklypear. The following table provides fire return intervals for plant communities and ecosystems where brittle pricklypear occurs. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Community or Ecosystem Dominant Species Fire Return Interval Range (years) bluestem prairie Andropogon gerardii var. gerardii-Schizachyrium scoparium 43,56] Nebraska sandhills prairie Andropogon gerardii var. paucipilus-Schizachyrium scoparium <10 bluestem-Sacahuista prairie Andropogon littoralis-Spartina spartinae <10 [56] silver sagebrush steppe Artemisia cana 5-45 [29,57,83] sagebrush steppe Artemisia tridentata/Pseudoroegneria spicata 20-70 [56] basin big sagebrush Artemisia tridentata var. tridentata 12-43 [61] mountain big sagebrush Artemisia tridentata var. vaseyana 15-40 [4,16,54] Wyoming big sagebrush Artemisia tridentata var. wyomingensis 10-70 (40**) [74,84] saltbush-greasewood Atriplex confertifolia-Sarcobatus vermiculatus 56] desert grasslands Bouteloua eriopoda and/or Pleuraphis mutica 10 to <100 [52,56] plains grasslands Bouteloua spp. <35 [56,83] blue grama-needle-and-thread grass-western wheatgrass Bouteloua gracilis-Hesperostipa comata-Pascopyrum smithii <35 [56,60,83] blue grama-buffalo grass Bouteloua gracilis-Buchloe dactyloides <35 [56,83] grama-galleta steppe Bouteloua gracilis-Pleuraphis jamesii <35 to <100 blue grama-tobosa prairie Bouteloua gracilis-Pleuraphis mutica 56] blackbrush Coleogyne ramosissima <35 to <100 Rocky Mountain juniper Juniperus scopulorum <35 [56] wheatgrass plains grasslands Pascopyrum smithii <5-47+ [56,57,83] pinyon-juniper Pinus-Juniperus spp. <35 [56] Colorado pinyon Pinus edulis 10-400+ [22,26,41,56] interior ponderosa pine* Pinus ponderosa var. scopulorum 2-30 [3,6,47] Arizona pine Pinus ponderosa var. arizonica 2-15 [6,19,64] mesquite Prosopis glandulosa <35 to <100 [52,56] mesquite-buffalo grass Prosopis glandulosa-Buchloe dactyloides <35 Texas savanna Prosopis glandulosa var. glandulosa <10 [56] mountain grasslands Pseudoroegneria spicata 3-40 (µ=10) [2,3] oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [56] blackland prairie Schizachyrium scoparium-Nassella leucotricha <10 Fayette prairie Schizachyrium scoparium-Buchloe dactyloides <10 [75] little bluestem-grama prairie Schizachyrium scoparium-Bouteloua spp. <35 [56] *fire return interval varies widely; trends in variation are noted in the species reviewBrittle pricklypear reproduces by seeds, layering, and sprouting from detached stem segments [68].
Breeding system: Brittle pricklypear is monoecious [9].
Pollination: Brittle pricklypear is pollinated by insects [9].
Seed production: Brittle pricklypear does not dependably flower every year in its northerly range, thus limiting seed production in these areas [9,48,79].
Seed dispersal: Seeds of brittle pricklypear are primarily spread when the fruits are eaten by frugivorous birds and small mammals. Fruits also readily attach to the fur and feathers of animals [8,68].
Seed banking: No information is available on this topic.
Germination: Germination rate is reportedly low for seeds of Opuntia species [71].
Seedling establishment/growth: Although the literature reports that brittle pricklypear regenerates by seeds [9], information is lacking on the specifics of seedling establishment and growth.
Asexual regeneration: Asexual reproduction occurs from detached pads which readily root even in the absence of water. The pads are primarily dispersed by attaching to animals by the barbed spines. The pads are also dispersed by gravity and by floating in water during heavy rains or snow melt. In the northerly range of brittle pricklypear, flowering can be rare and the plant may depend wholly on vegetative reproduction [9,48].
The scientific name of brittle pricklypear is Opuntia fragilis
(Nutt.) Haw. (Cactaceae) [9,21,38,39,45,80].
Infrataxa: Based upon differences in distribution and plant size, some systematists recognize 2 varieties
of brittle pricklypear [9,38,39,50,78]:
Opuntia fragilis var. brachyarthra (Engelm. & Bigelow) Coult, little pricklypear
Opuntia fragilis var. fragilis, pygmy pricklypear
Hybrids: Brittle pricklypear hybridizes with plains pricklypear (O. polyacantha) and
grizzlybear pricklypear (O. erinacea) [9].
Opuntia fragilis, known by the common names brittle pricklypear and little prickly pear, is a prickly pear cactus native to much of western North America as well as some midwestern states such as Illinois, Iowa, Wisconsin and Michigan. It also occurs in several Canadian provinces. It is known from farther north than any other cactus,[2] occurring at as far as 56°N latitude in British Columbia.[3] There is an isolated and possibly genetically unique population in Eastern Ontario known as the "Kaladar population".[4]
Opuntia fragilis is a small, prostrate plant, rarely more than 10 cm (4 in) high: joints tumid, fragile, easily detached, oval, elliptical, or subglobose, 3–5 cm (1–2 in) long and nearly as thick as broad, bright green: areoles 0.6–1.3 cm (1⁄4–1⁄2 in) apart, with whitish wool and a few white to yellow bristles, which are much longer and more abundant on older joints; spines 1–4, occasionally a few small additional ones, weak, dark brown, the upper one usually longer and stronger than the others, rarely 2.5 cm (1 in) in length: flowers greenish yellow, 2.5–3.2 cm (1–1+1⁄4 in) wide: fruit ovate to subglobose with few spines or bristles, mostly sterile, 2.5 cm (1 in) or less long; seeds few and large.[5]
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Opuntia fragilis var. denudata
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Opuntia fragilis var. denudata
A hybrid
Opuntia fragilis, known by the common names brittle pricklypear and little prickly pear, is a prickly pear cactus native to much of western North America as well as some midwestern states such as Illinois, Iowa, Wisconsin and Michigan. It also occurs in several Canadian provinces. It is known from farther north than any other cactus, occurring at as far as 56°N latitude in British Columbia. There is an isolated and possibly genetically unique population in Eastern Ontario known as the "Kaladar population".
