Thorns

Why do so many plants in the desert have thorns? I was expecting cactus to have thorns. That just seems part of the definition of being a cactus. But so many plants have thorns. There are thorns everywhere. You really need to stick to the walking paths unless you are wearing leather gaiters or chaps.

"Here's a pretty bush," I thought. Just your nice, standard bush.

Oops. Standard for the desert, that is.


The prickly pear cactus in my yard is a good example of why you don't want to trip and fall while gardening in your yard. Not a good thing.


I thought that thorns or spines would cut down on animals eating the cactus. But those thorns don't stop javalinas from eating the prickly pear cactus and other cacti. (Sorry, the best I could do was a photo of a javalina and prickly pear in the same shot. With all the sweet, new foliage around, the javalinas are leaving the prickly pear alone. They aren't dumb.)

All the evidence I can give is an example of a chewed up prickly pear. Somebody has been eating it, spines and all.

Outside of our front door, we have a beautiful bougainvillea. Given that this is the desert and it isn't watered a lot, it doesn't cascade like I've seen in California, but is still gorgeous. Why would bougainvillea need thorns? I guess they might help it cling to walls.

Want to cut some of those beautiful flowers? Wait a minute, look more closely. Really serious thorns.

Here's another sweet plant in my yard. It has that Dr. Seuss quality I love.

I reached down to touch it. Wait! Not so fast. That's some pretty serious armament.


Of course, there's the magnificent saguaro cactus. Thorns or spines don't stop the wildlife from making their homes in these cactus.



There's another classic "signature" plant of this region, the ocotilla, that has long branches with the blooms on the top like funny tassels. (The ones on the left side of the photo.) Another silly Dr. Seuss plant, I thought. (Did Dr. Seuss live in the desert?)



They make fences out of the long branches.


Do you know why nobody climbs those fences? Here's why.


There's a variety of cholla cactus, called jumping or chainfruit cholla, that even "throws" the spines at you if you get too close. Lucky me, this was not that kind of cholla. Ha, ha. It could have been a very different sort of day.



So here's your quiet, tree-lined path for morning walks. Nothing desert-like about this, right?

And here's one of those trees along this path. Pretty tree.

Look closely. Here's a close-up of a branch of that tree. The thorn is as long as my index finger, at least three inches. I mean these are industrial strength thorns. The whole tree bristles with them. Nobody's going to climb that tree any time soon.


So back to my original question. Why are is the desert full of thorns and spines? Why does every plant seem fully armed and loaded?

It doesn't have anything to do with us. It isn't personal. It's all about survival in the desert. Thorns and spines are just leaves adapted to the desert climate. Plants don't need flat leaves to get enough photosynthesis because there is plenty of light in the desert. I even read that, in the desert, spines and thorns conduct photosynthesis faster than flat leaves.

What do plants need to conserve in the desert? Water. Flat leaves lose tons more water than skinny leaves or, better, thorns and spines. Thorns and spines are the best kind of leaf where light is plentiful, but water is scarce.