Introduction

Opuntia engelmannii is found over much of trans-Pecos Texas, New Mexico, and Arizona; I also occurs in southwest Utah. It is the most common large opuntia and is routinely confused with other large opuntias. It is confused because many opuntias are difficult to identify, but also because few know about the other large species. The thinking goes that if it is a large Opuntia, it must be O. engelmannii.

The details

Opuntia engelmannii almost always has spines that are dark brown or black at their bases. The spine itself can be yellow-white, tan, or brown, but it is chalky and not translucent seeming or shiny. The plants are large, to 6- to 8-ft tall in warm climates with adequate water, but much smaller in cold climates.  They may be 3- to 4-ft tall and sprawl over many feet. The cladodes are typically green but may have a hint of blue-green.

The flowers are almost always yellow with a green stigma. Rarely a bit of red is present at the bases of the inner tepals. Most plants are spiny, but the gregoriana of southwest New Mexico types have few spines.