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Cactus are as evocative of the West as Sagebrush; the two even often grow near each other. Cactus are indigenous to the Western Hemisphere, are found in their greatest concentration along the Tropics of Cancer and Capricorn, and are native to every American state except Vermont and Maine. They are found in deserts, on seashores, in mountains, on plains, balds, and glades. Cactus come in a number of shapes, their flowers are often very large and attractive, their fruits are edible (some delicious, some not so), and they have evolved a number of structures and processes that make them perfectly at home in what we humans usually call "a hostile environment": They have a tough, waxy outer layer that reduces moisture loss; they produce chlorophyll not in leaves but in the outer cells of the stems; they convert absorbed water into a mucilaginous liquid that can be stored in large quantities in tissues capable of expanding; many Cactus root easily into new plants from broken pads/stems of older plants. "Cactus" is Greek for "prickly plant"; the word was used by Linnaeus in the 18th century to describe a prickly, thistle-like member of the Asteraceae Family found in Italy. "Cactus" was then used in the 19th century for the newly discovered spiny, drought resistant plants of the Western Hemisphere. |
The name "Opuntia" was used by Theophrastus for a plant, not in the Cactus Family, which grew near the Greek town of Opus. Somehow "Opuntia" was centuries later applied to a genus of Cacti. |
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Opuntia fragilis (Fragile Prickly Pear Cactus) Semi-desert, foothills. Sandy and rocky
openings. Summer. These low-growing, clump-forming Opuntia often spread in circles three to five feet in diameter. Pads of Opuntia fragilis break off very easily, commonly attach themselves to animals (including human animals), and are thereby widely disseminated. Pads can be plump like potatoes, flattened somewhat, or nearly cylindrical. Opuntia fragilis commonly hybridizes with other Opuntia and this accounts for its myriad of forms. This is an easily overlooked plant until it flowers yellow in late June -- or until you inadvertently pick up a segment on your trousers, shoes, or hands -- or have to pull a pad from your dog's fur. The third photograph from the top of the page shows new flower bud growth at the top of the pads and also shows five new pads with new, light red, small spines. Opuntia fragilis is easily confused with Cylindropuntia whipplei, for in our area the two are often low and spreading with long and narrow stems (pads) that can look very similar. Older plants can be easier to identify, for Opuntia fragilis stays low (to only 5 inches tall), whereas old Cylindropuntia whipplei plants can be more than a meter tall. Several characteristics help to separate the two species no matter what age they are. The most easily observed difference is in the bumps on the surface of the stems. These bumps are called "tubercles", from the Latin for "a bump or swelling", as in "tuber" and "tuberculosis". Opuntia species have no prominent tubercles; Cylindropuntia species have prominent tubercles. The pads of O. fragilis are somewhat flattened, potato-like and broad whereas the pads of C. whipplei are narrow and cylindric. Opuntia species have jointed pads; Cylindropuntia species do not have jointed pads. Cylindropuntia whipplei spines have a detachable, deciduous sheath. Opuntia fragilis spines do not have a sheath. The caveat for all the above is that Cactus species are notorious for their hybridization, so the above distinguishing characteristics do not always hold. Thomas Nuttall collected Opuntia fragilis in Minnesota, probably in 1810. He named it Cactus fragilis in his 1818 Genera of North American Plants (click the title to read), but the plant was renamed Opuntia fragilis by Adrian Haworth in 1819. |
Range map © John Kartesz,
County Color Key
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Range map for Opuntia fragilis |
Species present in state and native
Species present in state and exotic
Species not present in state
Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Eradicated
Questionable presence