Opuntia pottsii

Opuntia pottsii
Opuntia pottsii

Salm-Dyck, Cacteae in Horto Dyckensi Cultae Anno 1849 236, 1850

HerbariumHerbariumHerbariumHerbarium; Herbarium; Herbarium; HerbariumHerbarium (O. ballii); Herbarium (O. ballii)

What is Opuntia pottsii?

Opuntia pottsii is a small prickly pear cactus with colorful flowers. It is found in many regions of the West but it is seldom abundant. 

Details

Opuntia pottsii is a small prickly pear cactus, sometimes just 10 to 15 cm tall or 25 cm across. There are (0)1-4(5) spines per areole in the distal portion of the pad. Spines are gray-white to red-brown or rarely yellow, erect or reflexed, terete or proximal ones flattened, sometimes spirally twisted. Spines are slender and the longest may be over 4(5) cm. The cladodes of this Opuntia are dark green, cuneate-obovate to commonly rhombic, 5 to 15(20) cm long and 5 to 7(9) cm wide. The cladodes are fleshy but firm.

Flowers are reddish or pink (sometimes yellow). The style is whitish and the stigma is white to pale yellow. Anthers are yellow. Seeds are tan to gray, subcircular, thick and warped; the girdle protrudes about 0.5 mm. 

Some O. pottsii plants grow upright from a single central stem; the pads do not crawl along the soil as is often the case with many small Opuntia species. However, other forms are prostrate and resemble O. macrorhiza. Benson (Cacti of United States and Canada, 1983) proposed a very broad concept of O. macrorhiza that included O. pottsii as a distinct variety of that prickly pear cactus. In fact. while O. pottsii is variable, it clearly differs from O. macrorhiza by the flower color as well as the long pericarpels. There is enough variation within the species that varieties might be described, but these have not been formally published. A distribution map is provided by the Flora of North America online, but the map is conservative because this prickly pear cactus has been observed in more northerly and more easterly areas by the authors. In fact, O. pottsii  occurs in northwestern AZ. 

The plants can be confused with other small opuntias including O. polyacantha and O. macrorhiza if they are only casually observed or if they are growing among grasses, etc. However, O. pottsii is noticed in flower because it has pink, red, orange, or salmon flowers (some plants have yellow flowers). Britton and Rose reported that the type locality for this prickly pear cactus is near Chihuahua, MX. See the original description. Opuntia pottsii is tetraploid.

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