Pondering Purple Cholla

Walking around the bajada at Sabino Canyon this winter, I kept noticing that some of the cholla cacti are purple or reddish in color, while most of the other plants are green. After doing a little research, I learned that it is not uncommon for buckhorn and staghorn chollas to take on a purple or red tinge in cooler weather or drought.

But not all of the buckhorn and staghorn chollas turn purple, it depends on the hybrid or microspecies. Below are two staghorn chollas growing close to each other; one is clearly purple while the other is green.

I found that some chollas have purple stems, and green stems, as well as mixed purple and green branches, all on the same plant.

Cactus wrens often perch on the stems of buckhorn and staghorn cholla cacti, but prefer not to build nests in them. It is teddybear and chainfruit chollas, whose branches are more spiny, that cactus wrens like to use for nesting sites. Fortunately, the branches of buckhorns and staghorns do not detach as easily as teddybear chollas, so you can brush against them without getting stuck...usually.

Buckhorn (Opuntia acanthocarpa) and staghorn chollas (Opuntia versicolor) can be tricky to tell apart because they look similar. Both species bloom in a wide variety of colors including red, orange, yellow, pink, purple, green or bronze. Buckhorn flowers are slightly larger than staghorns. There is one noticeable difference: the long filaments inside the flowers of buckhorn chollas are dark red, while the filaments of staghorn cholla flowers are yellowish green.

So, then how do we know which cholla is which, in the winter when there are no flowers present? The fruit persists on buckhorns for several months and staghorn fruit stays on the plant a year or longer. The Arizona-Sonora Desert Museum's A Natural History of the Sonoran Desert says that when buckhorn fruit is mature, it's spiny and "dry and deeply tuberculate" which I would just describe as shriveled and bumpy-looking like these:

Buckhorn cholla fruit

Staghorn fruit (pictured below) starts out bumpy, but becomes smoother and more rounded when mature. And, staghorn fruit is usually spineless.

Staghorn cholla fruit

An easy-to-remember way to tell the two cacti species apart by their fruit:

buckhorn and bumpy begin with the letter "b"
and staghorn and smooth start with "s."

Now that we know how to identify these purple chollas, let us simply enjoy the beautiful variations in plant heights, colors, branching angles, fruit shapes and colors. Here are a dozen images of reddish or purple colored buckhorn or staghorn chollas at Sabino Canyon in winter:

Click on any photo to enlarge.

I hope you enjoyed exploring these purple Sonoran Desert cacti with me in the wintertime. I'm looking forward to checking out all the different colors of buckhorn and staghorn cholla cactus flowers in the spring.