Last night I dreamt of rain, suspecting upon awakening that I was not alone in this fruitless endeavor. We are in an exceptional drought. Clouds, let alone rain, seem like a mere mirage of the mind now. Still, anyone with a keen eye can find a whole host of species that thrive despite drought conditions. Many local wildlife species, from the smallest invertebrate to sizable vertebrates, possess a slew of adaptations to help them cope with a lack of water in their various habitats.
Still, my vote for “best-adapted to drought” unequivocally goes to our native succulents. Further, November is a time when they tend to stand out amidst the rather dun and dull landscape. Getting to know them is certainly worth your while.
What exactly is a succulent? Namely, a plant species that sequesters water in one or more of its structures, such as stems, leaves, or roots. The evolution of succulence has enabled a number of plants to literally weather the otherwise withering droughts that so often punctuate our local climate. Once precipitation – rain or snow – arrives, the succulents quickly slake their thirst by making the most of this temporary surfeit of moisture.
Since herbivorous wildlife is often in need of water, eating a succulent might seem a plausible solution. Yet many succulents produce such vile toxins that all but the hardiest herbivores are excluded from this would-be banquet – except collared peccaries that is! Finally, not all succulents are equally succulent, meaning that they range from being able to harbor moderate to sensational amounts of water, as well as every level in between.
Quite naturally many Arizonans equate succulents with the cacti. Repeat after me: “all cacti are succulents, but not all succulents are cacti!” This little phrase sorts things out on a gross level at least, leaving the possibility that plants not in the cactus family can be succulent as well.
One local plant that is often mistakenly called a cactus is the ocotillo. When precipitation saturates the upper soil, the mostly shallow roots of ocotillo efficiently absorb as much as they can, storing it mostly in their stems.
Like many of our succulents, the ocotillo evolved in the tropics and doesn’t actually do much with its stores of water until spring and summer arrive. In spring, magnificent crimson blossoms punctuate the terminal stem tips. A wide range of species visit the flowers, including ants, bees, hummingbirds, pyrrhuloxias, and Lucy’s warblers. Throughout spring and summer ocotillos produce rather succulent leaves as their stores of water permit, losing them when soil moisture evaporates beyond critical levels.
Another set of non-cacti succulents are various members of the asparagus family – the yuccas, agaves, and their relatives. All of them are leaf succulents. They too are mostly inactive when things are cold, but spring to life in May and June.
Agaves take succulence within the family to extremes. Palmer agave – our largest native species – may take from 10 to 25 years to initiate flowering. This is owing to its need to accumulate water stocks and hence the sugars that result from them, which in turn furnish them the energy to produce their behemoth flowering stalks.
As with ocotillos, the blossoms of agave benefit a broad spectrum of wildlife – nectar-feeding bats, hummingbirds, wasps, orioles, etc.
We end with the cacti – our most famous stem succulents. Southern Arizona hosts a spectacular variety of species in this unique family. While other plant families may also be exclusively succulent, no others take this adaptation to such extremes. A good soil soaking can result in a significant weight gain by prickly pears, chollas, barrel cacti, giant saguaros and the like. Saguaros are famous for their ability to imbibe water quickly from their shallow roots. The pleats in their stems allow for significant expansion to the point where even one good storm may lead to the addition of tons of water to the plant’s structure.
So, yes, we are in a drought, but by the same token are we ever succulent!
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit: www.ravensnatureschool.org