Origin and Habitat: This is a wide-ranging species. It can be found in Mexico (Chihuahua), United States (Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, Washington, Wyoming), and Canada (Alberta, British Columbia, Saskatchewan). The species is very abundant throughout its range.
Altitude range: It grows at elevations of 300 to 2,400 metres above sea level.
Habitat and Ecology: The species is found in grasslands, pine-juniper forests, sagebrush, xerophyllous scrub and lower montane forest. It grows on sandy soils of flats, washes, canyonsides, and hillsides in the desert, in woodlands, and on plains. Seeds of plains pricklypear fall near the parent plant or are dispersed by mammals that consume the fruits. They are also dispersed when barbs on the fruits or lobes attach to a passing large mammal. Opuntia polyacanthaSN|31216]]SN|31216]] lives in fire-prone habitats, mortality after a fire is often greater than 50%, but rarely total. Plants regenerate by sprouting from the root crown, by layering of unburned or partially burned stem pieces that contact soil, and from seedling establishment. This pricklypear provides food for many types of animals. It provides over half the winter food for the black-tailed prairie dog in one area. Pronghorn deer eat it, especially after the spines are burned off in wildfires. There are no major threats to this species. A potential threat to species of the genus Opuntia is the invasion of the cactus moth Cactoblastis cactorum, which can exterminate populations completely. Several other insects attack the cactus, including the cactus moth Melitara dentata, the blue cactus borer Olycella subumbrella, and the cactus bug Chelinidea vittiger.

• Opuntia polyacantha Haw.
• Cactus ferox Nutt.
• Tunas polyacantha (Haw.) Nieuwl. & Lunell

• Opuntia polyacantha Haw.
• Cactus ferox Nutt.
• Tunas polyacantha (Haw.) Nieuwl. & Lunell
• Opuntia barbata K.Brandegee ex J.A.Purpus
• Opuntia heacockiae Arp
• Opuntia media Haw.
• Opuntia missouriensis DC.
• Opuntia polyacantha var. juniperina (Britton & Rose) L.D.Benson
• Opuntia juniperina Britton & Rose
• Opuntia polyacantha var. rufispina (Engelm. & J.M.Bigelow) L.D.Benson
• Opuntia missouriensis var. rufispina Engelm. & J.M.Bigelow
• Opuntia polyacantha var. trichophora (Engelm. & J.M.Bigelow) J.M.Coult.
• Opuntia missouriensis var. trichophora Engelm. & J.M.Bigelow
• Opuntia missouriensis f. trichophora (Engelm. & J.M.Bigelow) Schelle
• Opuntia trichophora (Engelm. & J.M.Bigelow) Britton & Rose
• Opuntia rhodantha K.Schum.
• Opuntia erinacea var. rhodantha (K.Schum.) L.D.Benson
• Opuntia rutila Nutt.
• Opuntia splendens Pfeiff.
• Opuntia ursus-horribilis Walton

• Opuntia polyacantha var. albispina (Engelm. & J.M.Bigelow) J.M.Coult.
• Opuntia missouriensis var. albispina Engelm. & J.M.Bigelow
• Opuntia missouriensis f. albispina (Engelm. & J.M.Bigelow) Schelle

• Opuntia polyacantha var. arenaria (Engelm.) B.D.Parfitt
• Opuntia arenaria Engelm.

• Opuntia polyacantha var. erinacea (Engelm. & J.M.Bigelow) B.D.Parfitt
• Opuntia erinacea Engelm. & J.M.Bigelow
• Opuntia hystricina var. bensonii Backeb.
• Opuntia polyacantha subs. erinacea (Engelm. & J.M.Bigelow) Guiggi
• Opuntia erinacea var. ursina (F.A.C.Weber) Parish
• Opuntia hystricina var. ursina (F.A.C.Weber) Backeb.
• Opuntia ursina F.A.C.Weber

• Opuntia polyacantha var. hystricina (Engelm. & J.M.Bigelow) B.D.Parfitt
• Opuntia erinacea var. hystricina (Engelm. & J.M.Bigelow) L.D.Benson
• Opuntia hystricina Engelm. & J.M.Bigelow
• Opuntia rhodantha var. xanthostemma (K.Schum.) Rehder
• Opuntia erinacea var. xanthostemma (K.Schum.) L.D.Benson
• Opuntia xanthostemma K.Schum.
• Opuntia utahensis J.A.Purpus

• Opuntia polyacantha var. nicholii (L.D.Benson) B.D.Parfitt
• Opuntia hystricina var. nicholii (L.D.Benson) Backeb.
• Opuntia nicholii L.D.Benson

• Opuntia polyacantha var. platycarpa (Engelm.) J.M.Coult.
• Opuntia missouriensis var. platycarpa Engelm.
• Opuntia polyacantha f. platycarpa (Engelm.) Toumey & Rose

• Opuntia polyacantha var. schweriniana (K.Schum.) Backeb.
• Opuntia schweriniana K.Schum.

Description: The plains prickly pear, Opuntia polyacanthaSN|31216]]SN|31216]] is a low shrubby spreading perennial plant with many branches, up to 10-20 cm (-40) centimetres tall, usually forming small clumps or mats of pads which may be 2–3 metres wide. . Mats up to 3.7 m in width and 9.15 m long were observed in the Great Plains. Prickly pear plants usually live less than 20 years, but vegetative propagation can ensure a very long life span for the clonal colony.
Roots. Fibrous, shallow, laterally extensive that takes advantage of rainfall as scant as 2.5 mm.
Stems segments: ± prostrate branches with stems segments not easily detached, succulent, flattened, low tuberculate, not very thick less than 1 cm thick, glabrous, oval or orbicular, 4-18(-27) centimetres wide, (2-)3.5-12(18) cm wide,, but usually less than 10 cm in diameter, generally light green or blue-green.
Areoles: Small, closely set, 4-14 per diagonal row across midstem segment, usually less than 1 cm apart, subcircular, 3-6 mm, tipped with tan to brown woolly brown fibres and yellow or reddish glochids. Many of the areoles have spines which are quite variable in size and shape.
Spines: Numerous (0-)6-10(-18) mostly or only on the distal areoles of stem segment, only slightly barbed, stout or thin, straight or curling downward or bent backward, and any of a variety of colours, 0.4 to 18.5 centimetres in length, those from the sides mostly short, appressed, but often 1 or 2 of these elongated and like those from the upper and marginal areoles. Spines of 1 or 2 kinds; if 1 kind: 0-18 per areole, spreading and curling in various directions, 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.
Flowers: Small, yellow to magenta, 2.5 to 6 cm long, including the ovary, 4.5-8 cm
in diameter; sepals tinged with red; petals lemon-yellow, orange pink or magenta; filaments white, yellow, or red to magenta (flowers may superficially appear bicolored), anthers yellow; style white to pale pink stigma lobes green.
Blooming season: Late spring to early summer, for 3-4 weeck. Individual flowers open from 7-11 hours per day.
Fruit: Dry at maturity, oblong, to cylindrical, tan to brown, 15-45 mm long, 12-25 mm wide, areoles 10-33, each or only distal areoles bearing small clusters of white, acicular barbed spines. Fruits develop on stem lobes. Fruits ripen approximately 2-1/2 months after flowering.
Seeds: White, tan to grey, flat, warped, oblong to subcircular, and about 3-7 mm long, 2-4 mm wide, acute on the margin; girdle protruding 1-2 mm. The number of seeds varies from none to more than 70 per fruit. The most fruit is produced on stem branches that are 6 to 8 years old.
Taxonomic notes. Many varieties of O. polyacantha have been described but usually only these 5 are recognized: var. polyacantha, var. arenaria, var. erinacea, var. hystricina, and var. nicholii (Parfitt 1991). Populations of Opuntia polyacanthaSN|31216]]SN|31216]] with spines few or absent (especially var. hystricina) were the basis for several names including O. juniperina, O. utahensis, and O. rhodantha.

Bibliography: Major references and further lectures
1) Heil, K., Terry, M. & Corral-Díaz, R. 2013. Opuntia polyacantha. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 26 May 2015.
2) N. L. Britton, J. N. Rose: “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Vol I, The Carnegie Institution of Washington, Washington 1919
3) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
4) Abrams, L. 1951. “Geraniums to Figworts.” 3: 866 pp. In L. Abrams Ill. Fl. Pacific States. Stanford University Press, Stanford.
5) CONABIO. 2009. “Catálogo taxonómico de especies de México.” 1. In Capital Nat. México. CONABIO, Mexico City.
6) Flora of North America Editorial Committee, e. 2003. “Magnoliophyta: Caryophyllidae”, part 1. 4: i–xxiv, 1–559. In Fl. N. Amer. Oxford University Press, New York.
7) Gleason, H. A. 1968. “The Choripetalous Dicotyledoneae.” vol. 2. 655 pp. In H. A. Gleason Ill. Fl. N. U.S. (ed. 3). New York Botanical Garden, New York.
8) Gleason, H. A. & A. J. Cronquist. 1991. “Man. Vasc. Pl. N.E. U.S.” (ed. 2) i–910. New York Botanical Garden, Bronx.
9) Great Plains Flora Association. 1986. “Fl. Great Plains” i–vii, 1–1392. University Press of Kansas, Lawrence.
10) Hitchcock, C. H., A. J. Cronquist, F. M. Ownbey & J. W. Thompson. 1961. “Saxifragaceae to Ericaceae.” Part III: 614pp. In Vasc. Pl. Pacif. N.W.. University of Washington Press, Seattle.
11) Moss, E. H. 1983. “Fl. Alberta” (ed. 2) i–xii, 1–687. University of Toronto Press, Toronto.
12) Scoggan, H. J. 1979. “Dicotyledoneae (Loasaceae to Compositae).” Part 4. 1117–1711 pp. In Fl. Canada. National Museums of Canada, Ottawa.
13) Wikipedia contributors. "Opuntia polyacantha." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 2 Apr. 2015. Web. 26 May. 2015.
14) Parfitt, Bruce Dale. 1991. “Biosystematics of the Opuntia polyacantha complex (Cactaceae)” of western North America. Tempe, AZ: University of Arizona.
15) Turner, George T.; Costello, David F. 1942. “Ecological aspects of the pricklypear problem in eastern Colorado and Wyoming. Ecology.” 23(4): 419-426.
16) USDA Plants Profile for Opuntia polyacantha (plains pricklypear)
17) Johnson, K. A. 2000. “Opuntia polyacantha. In: Fire Effects Information System”, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer) <http://www.fs.fed.us/database/feis/plants/cactus/opupol/all.html>
18) Opuntia polyacantha. "Flora of North America." http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242415223 Retrieved 26 May. 2015.

Cultivation and Propagation: Opuntia polyacanthaSN|31216]]SN|31216]] is a low maintenance plant that tolerate considerable neglect and will naturalize. Easy to cultivate outdoor in dry, sandy or gravely, well-drained soils. May be grown in clay soils as long as drainage is good and soils do not remain wet, it is very adaptable both in acid, neutral and basic (alkaline) soils, but prefers a pH in the range 6 to 7.5. No serious insect or disease problems. Can tolerates strong winds but not maritime exposure.
Watering Needs: Must be kept fairly dry in winter but likes a reasonable supply of water in the growing season, tolerate dry condition but suffer if exposed to prolonged and severe drought. A position at the base of a south-facing wall or somewhere that can be protected from winter rain is best for this plant, but is however resistant to moisture and rain.
Sun Exposure: Full sun (only), in semi shaded position wont produce many flowers.
Frost Tolerance: Not frost tender. Plants are very cold-hardy, tolerating temperatures of -12° to -45° C (depending on clone) , they are also quite tolerant of winter wet. (In good drained soils)
Propagation: Propagated by cuttings of leaf pads at any time in the growing season: previous year's pads may be severed at the joint during the growing season, dried for a week to ensure that the base is thoroughly dry and then planted directly in the garden (joint wound down) or in a potting medium. May also be grown from seed with moderate difficulty. Seed - sow early spring in a very well-drained compost in a greenhouse. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for at least their first two winters. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Give the plants some protection from winter wet. Make sure you have some reserve plants in case those outdoors do not overwinter.
Known hazards: Opuntia polyacanthaSN|31216]]SN|31216]] pads are covered spines and in numerous nasty barbed glochids (little prickles) not so much sharp and spiny as persistent and irritating. These glochids are easily dislodged when the plant is touched and then become stuck to the skin where they are difficult to see and remove, can cause considerable discomfort. Need a little care in handling.
Medicinal uses: Glochids, spines, and stem joints of Opuntia polyacanthaSN|31216]]SN|31216]] are used medicinally, and the mucilage in stems has been used to stabilize fabric colouring and clarify drinking water.
Horticultural uses: Rock gardens, raised beds, stone walls, sandy slopes, dry prairie, small area ground cover, pots.
Propagation: The cactus reproduces by seed, by layering, and by resprouting from detached segments.