Tuesday, 7 October 2014

Close encounters with the Teddybear Cholla

The sign was clear. Don't touch. Don't even think about touching the Cylindropuntia bigelovii, even though its common name is the Teddybear Cholla (pronounced choy-yah).

So I picked up a small piece. Swore. Flicked it onto my foot where it attached itself securely to the front of my shoe. I eventually managed to scrape it off on a rock and then break the remaining spines back to the rubber in my shoe. This was two weeks ago, while in the Joshua Tree National Park south-east of Los Angeles. The spiny remnants reside in my shoe still today.

Back in the desert as temperatures hit 96 degrees F (around 36 degrees C) in what is quite appropriately called the Cactus Garden, Lynda mumbled something about signs and kids. I licked my wounds.

The Teddybear Cholla is by far the most common species of cactus in the park and pretty successful at getting around. It's a close relative of the prickly pear and in fact used to be included in the same genus, Opuntia. The most obvious difference is that the chollas (there are others in this group) have cylindrical stems (i.e. the green blades that make up most cacti) while the prickly pears are flattened ones.

The spines are also different, as I experienced. Many opuntias (as I can also attest) have clumps of tiny 'glochids' which look innocuous but persist and irritate long after any contact with the cactus. The chollas have pretty obviously aggressive spines and you'd be an idiot to even touch them.

The Teddybear Cholla is also called the Jumping Cactus due to its propensity to find its way from the ground to some part of our body. It can seem at times like it jumps at you. All these detached bits and pieces readily root and settle in as new plants, sometimes after being transported rather long distances (e.g. to Australia; although I should say that personally I may have carried fragments of spines, but not flesh of the cactus).

I gather the easiest way to remove the reverse-barbed spine from your skin is to use a comb and to 'quickly jerk it away'. I wasn't carrying a comb and in any case, due to the force required I gather there is also a risk it flies straight into your companion, making a fresh connection.

A mature specimen is about one to two metres tall, with the base becoming trunk like with age as lower branches die and fall off. The spines cover pretty much the entire surface of the plant, which must make it difficult for sunlight to reach the green photosynthetic tissue. Presumably protection from desiccation and predation are more important.

Young spines are yellow. Old ones black. Yellow-green flowers appear in spring with the fruits, as illustrated here from mid-autumn, mostly without fertile seeds. It does nicely without resorting to sexual reproduction it seems. In fact according to the Arizona-Sonora Desert Museum, many plants have three rather than two sets of chromosomes, and are completely sterile. These sterile plants can still cover up to two square miles desert excluding nearly all other plants.

This species is common in the Mohave Desert and hotter parts of the Sonoran Desert, both of which intersect in the Joshua Tree National Park. And I can't really post about the Joshua Tree National Park without a picture of the striking Joshua Tree (Yucca brevifolia) so here it is!

Notes: Thanks Lynda for the final picture, and yes I lied when I said my last post was the final one from my US holiday. This one, almost certainly, is. 


Anonymous said...

Tim the reason this is such a friendly plant is that the glochids and spines are barbed so they do not come out cleanly even with a comb but they certainly are a magnificent site, especially if back lit by late afternoon sun.

Tim Entwisle said...

Thanks Wayne. Yes I gather it has barbs so even the comb technique must just wrench them out... Not pleasant from that perspective, but pleasant to look at that's for sure.