Opuntia macrorhiza (Plains Prickly Pear)
|Also known as:||Twist-spine Pricklypear|
|Habitat:||part shade, sun; dry prairies|
|Bloom season:||May - July|
|Plant height:||2 to 12 inches|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are showy, 2 to 3 inches across, with 7 or more yellow petals that are sometimes reddish at the base. A green ovary protrudes in the center, surrounded by numerous yellow or red stamens with yellow tips. There may be 1 to several flowers around the tip end of a pad.
Leaves and stems:
With cacti, the spines are modified leaves and the fleshy pad segments are modified stems. Spines are up to 2½ inches long and typically straight, clustered in groups of 1 to 6, growing from numerous small projections (areoles) on the surface of the pad. The spines are not hooked but the areoles have tiny barbs (glochids) at the base of the spine cluster that easily detach and can be difficult to see, let alone remove once embedded in skin. The pads are a dull dark green to blue green, generally a flattened round, oval or egg shape, 2 to 5 inches long and 2 to 4 inches wide with a waxy surface. The segments do not easily detach from each other. Plants can form a mat up to 5 feet across.
There are 2 species of prickly pear cactus native to Minnesota, one of which is Brittle Prickly Pear (Opuntia fragilis), though there is confusion and debate over the name of the second species. Some call it O. humifusa, others O. macrorhiza., and still others are unclear whether these are actually distinct and separate species. In the meantime, the DNR lists O. macrorhiza so that's what we're going with. A rose by any other name...? The flowers of the 2 natives are more or less the same. Distinguishing features are mostly the size and shape of the pads and number of spines. Brittle Prickly Pear has much smaller pads that easily detach and up to 8 spines per areole. Plains Prickly Pear is way overlooked as an interesting garden species. It will thrive in any hot summer location, from clay to sandy soils, as long as site is hot and well drained. New starts are easy—just cut off and root a year old pad, any time of year. It also germinates readily from seed though maturation period is numbers of years. I've used long handled forceps and leather gloves to get at weeds growing between the pads—dangerous work, but worth it!
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Photos courtesy Peter M. Dziuk, taken in Renville County, along a country road in North Dakota, and in a private garden in Lino Lakes
Have you seen this plant in Minnesota, or have any other comments about it?