Opuntia nicholii is an uncommonly encountered prickly pear cactus occurring in isolated locations in far northern Arizona and adjacent southern Utah.
O. nicholii can be large and sprawling, stretching up to 2 m across. Cladodes are obovate to narrowly obovate and 10-20 cm long. Major spines are 4-12 cm long and stout and generally occur in every areole. Longer spines (1-5) are down curved, ascending, and pink-gray or the lower portion gray to black.
Flowers are yellow and 5-8 cm across. Fruits are 2-5 cm long and spiny. Seeds are large.
The Flora of North America reports that O. nicholii grows in “barren areas with saltbush and ephedra, limestone or red, sandy soils,” around 4000 ft. Some plants of O. nicholii vary from typical spination; perhaps through introgression with O. phaeacantha or O. aurea.
Even though the plants are large, some botanists proposed that O. nicholii was a variety of the smaller O. polyacantha rather than a distinct species. However, O. nicholii is hexaploid, whereas O. polyacantha is tetraploid. Like O. polyacantha, the fruits of O. nicholii are dry at maturity and the seeds are large.
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O. nicholii makes a superb garden plant due to is spiny nature and interesting sprawling branches.