Leafing so soon?

There are leaves and then there are leaves. And then there are cactus pads, like this wide flat prickly pear cactus pad, which are more like stems than leaves.

Because if you look closely, on the surface of this pad, you will see the actual leaves, small succulent pointy cones, next to their associated thorns, which form in the axil (that’s like the armpit!) of the leaves.

The thorns persist, as most desert dwellers know too well, but the little leaves fall off in a matter of days, another water-saving feature, so only the thorns and the thick-skinned pads, and the quickly hardening new pads, remain.

Stems or not, the pads, after the skin and thorns are very carefully removed, have been used for centuries as food by native civilizations in the desert

 

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Leafing again: the strange case of the ocotillo

One of the odder native residents of the Sonoran desert is the ocotillo bush. It typically consists of several spindly branches, vertically striped and spiny, up to 20 feet tall, that are leafless for long periods, only to sprout thick lines of small leaves within a few days after a rain.

Ocotillo branches with few leaves

Its desert adaptation of dropping leaves and playing possum is so complete that ocotillo plants for sale, in their leafless phase, with their branches tied in a bundle and roots bare, look thoroughly dead.

Ocotillo branches with many leaves

In the spring, they produce numerous red tubular blossoms at the ends of the branches that attract insects and birds of many species. They make great landscape plants because of their sparse sculptural look, and extremely low water requirements, and striking seasonal changes.

A thorny issue

Related to the last post, it is amazing how many kinds of thorns, bristles, hooks, spikes, prickers, sharp edges, pointed leaves, pointed branches, as well as claws, scales, fangs, spines, and hooves you find in the Sonoran desert, and generally in the arid western USA.

In a contrary kind of way, almost all of these indicate that there’s probably a nice, juicy, succulent hunk of flesh nearby.

But you’ll get hurt if you try to get at it!

Why does the cactus look like that?

The first thing you notice about a cactus is generally the spines. Some have short, nasty little almost invisible fishhooks, some inches-long needles. Then there’s the form of the plant. Most cacti are plump, rounded, often stubby. They tend to be grayish-green in color. And they usually do not have obvious leaves.

Why?

Whenever you come across questions like this, think about the ecosystem where the organism lives. Cacti live in dry climates with a lot of sun, and few other plants, especially leafy ones.

So keeping cool is an issue. A light neutral color does not absorb a huge amount of the sun’s heat. There are very few plants with dark bark, or skins, or leaves in the desert.

Retaining moisture is perhaps the most important issue for a desert plant. The blunt, compact shape of cacti, their thick skins, and lack of leaves are all moisture-conserving features.

And lastly, toothsome, moist leaves would attract all kinds of herbivores. So the lack of leaves discourages plant-eaters, and the big spines and tough hide protect any soft, moist tissue a cactus does have.