Haboob, the Desert Dust Storm

Another limiting factor in the desert arises from the ferocious dessicating and abrasive desert dust storm called the Haboob. Often associated with the seasonal monsoons, these storms can actually happen any time of year, blasting and scouring any plants and animals in their path.

The word haboob is Arabic, from the home of truly impressive sandstorms, but now is applied in any area susceptible to them.

These storms can move particles of dust and even sand, and may reach hurricane force for a few minutes at a time.

Deserts have few trees to stop the wind, and little moisture to hold down the soil. A haboob forms when warm air rises into thunderheads, then the air is cooled by rain, the storm collapses, and the cooled air falls and rushes out from the base of the storm, driving dust and sand before it, sometimes at truly remarkable speeds. Within minutes, winds can go from zero to 50 miles an hour.

Dust storms often arise suddenly, making them hard to avoid or escape. Most years in the Sonoran desert, there are traffic accidents associated with dust storms, when visibility suddenly plummets.

Desert plants need either shelter or thick skins to handle the dessication and scouring associated with a haboob or other winds.

A Dry Heat

The joke is, in the Sonoran desert, even though it’s 114, it’s a dry heat.

The idea being that with very low humidity, amazingly, under 5 percent at times, the heat is easier to bear.

114, an average high for a few days each summer, is still bad enough, but given how few trees and other shelter there is in the desert, it’s almost always a sunny heat during the daytime, which adds another 7 to 10 degrees.

All plants and animals and people that live in the desert need to be built or adapt in some way to survive these extreme temperatures.

The hottest time of year is a few days before the summer Solstice on June 21, and a few weeks after that. Then the average daily temperature starts going down again, very very gradually.

A few weeks after the solstice is also the time when the summer monsoons really get going. The standard definition of monsoon season is the change in the wind, but in the desert, the important thing is that the monsoon usually brings moisture and finally rain from the Gulf of California and the Gulf of Mexico.

And of course, when the humidity goes up and the rains start, it’s still over 100 degrees in the desert. And it’s no longer a dry heat.

Ocotillos in bloom

It is mid-April and the ocotillos are in bloom in the Sonoran desert, a great sight to see.

These plants can leaf out several times a year after rains, but they only bloom once a year, the blossoms providing food for a variety of insects and birds.

Plant vegetables NOW?

Now that we’ve had another hard freeze in the Sonoran desert that burned the tops off many shrubs, and melted tomato and pepper plants down to the ground, February may finally be time to plant again. But have your frost covers ready, just in case.

Tomato and pepper seedlings need to be transplanted now to give them a chance to ripen before the summer heat bakes them.

And all kinds of salad greens and onions can be planted as seeds or seedlings for a good crop. If you plant seedlings of lettuce, beets and chard, they will begin producing salads within a week or two, and continue into early summer.

Snow in the desert

Snow showers in the Sonoran desert, 30 December, 2010, after two days of rain. Rare treats.

Autumn desert vegetable garden

Into October now, it is already getting late, but perhaps a reminder for next year–fall is the other good time to start a food garden in the desert.

You will probably not have much success with foods that need to flower and fruit, but for leafy greens, this is a great time.

Chard, spinach, beet greens, herbs, all these can still be planted in the desert in October. Of course, they will need hand watering or irrigation. But some will produce right through the winter, depending on your location.

Some will go dormant, then revive in late January and February, when the longer daylight and warmer temperatures begin to return, the time when you can begin adding your regular spring vegetables.

Limiting factors in the desert

In some ways the term “limiting factor” is almost a definition of deserts, because deserts lack one or more essential ingredients for the survival of most kinds of plants and animals.

First, a desert is, by definition, a place with very little available water, either because there is little rainfall, or because it evaporates so fast. It may also be that most of the precipitation is unavailable because it is frozen most of the year, as in the far north or south, or in some high altitude regions.

Some areas may get bursts of moisture, even flooding, but it is episodic and not dependably available most of the year.

Temperature is another limiting factor. Many deserts get too hot for most organisms. Some deserts near the north and south poles are too cold. And yet others have wide swings in temperature.

Wind is another. There are few trees or shrubs to stop the wind. Desert mountains, river-courses or other sheltered areas may harbor small oases in their wind and sun shadows.

One unusual limiting factor is lack of sunlight. This can occur in deserts near the poles.

Especially interesting are the adaptations that plants and animals have developed to deal with these limiting factors. Many of them are what we talk about here.

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.

Choose native plants for your desert landscape

One way to figure out what plants will be suitable and attractive in your desert landscaping is to go to a nearby natural area and see what is growing wild.

Make sure you select a location that is similar to yours in exposure, dryness and altitude.

Take photos or make a list of plants you find attractive. Never dig up native plants! They are fragile and rare, and in most places it is illegal to do so.  Almost everything you will see is available in plant stores. Photos will also help you arrange your landscaping, showing which plants grow together, and how much space they need.

Then go to the web or in plant books to learn about the plants you have found, or take your photos to a local nursery that specializes in native plants, and decide which are for you.

The variety of desert plants is surprising: cacti, shrubs, vines, spring-flowering annuals, many kinds of perennials. A big virtue of native plants is that they  require little in the way of extra water and plant food, and are easy to maintain.

One thing to keep in mind about native plants–some of them grow very slowly, so it may take a while for your landscape to mature. But there is nothing to match their beauty, and their ability to attract native fauna.

On little coot feet

The American coot looks like a little round black duck. With a white snoot. And mad red eyes.

But it is not, not a duck.

After you look for a while, it also looks like a young chicken, a pullet, with a football shape, but rounder than a football.

A chicken, getting warmer.

Coots are in fact related to chickens, and more closely, to mudhens. (Go Toledo!)

While we think of them as northern wetland animals,  you can actually find them in the Sonoran desert, on some of the occasional lakes in the desert. They swim around, most often in pairs, and dive to gather vegetation, and the, um, scum from the bottom that they eat.

But the most amazing thing about coots is their feet. They have very strange feet. Not just plain chicken feet. But not duck feet, webbed paddling feet either.

They have these strange little flaps on the sides of their toes, very clever flaps actually, that make their toes very wide when they step down, or when they push against the water, but fold up to slender claw-width when they lift their feet, or bring them forward in the water, or take off in flight.

They are not easy to spot– you have to be quite close, or have the coots pose just right, then you can see them.

So if you see a round black swimming chicken-duck-bird with a white bill-beak and crazy red eyes, make sure you look for their really crazy black and gray flapped coot feet.