Mulch, in many forms, is crucial

By Angela O'Callaghan

Wednesday, Aug. 12, 2009 | midnight

Plants that are well adapted to our kind of landscape are a hardy lot – able to withstand lack of water, salty soil and intense sunlight. Once they become part of the landscape design, even these need a certain amount of care, of course.

With experience, desert gardeners have learned several "secrets for success," and among the most important is mulch.

Mulch comes in many forms; some are perfect for desert plants, while others meet the needs of the more tender ones. The fact is — all plants benefit from some kind of mulch, as long as it is the right kind.

Many home landscapes are dominated by rock. Not everyone likes this as a look, but even that broken gravel is a mulch. If you were to go out to the desert and look at the ground, you would not see much bare soil. Rather, you would see "desert pavement" — rocks that are firmly settled in the soil surface. This helps to keep dust down, moderate temperatures and help the soil beneath to stay a trifle cooler.

Rock in the home landscape follows the same principle as this desert pavement. Heat and direct sunlight bounces off lighter colored gravel, resulting in cooler soil during the day. Even desert natives or desert-adapted plants can grow better under these conditions. The down side of this kind of system is that the reflected heat can result in a hotter environment just above the mulch. Plants might require a little more water in this case, and this is why non-desert plants are generally not surrounded by rock mulch.

Sometimes intrepid desert gardeners will break their own rules and grow plants that are not so tough – ones that prefer a little more moisture and slightly cooler temperatures. Non-desert plants thrive when the soil around them is covered by what we call "organic" mulch. This means that the material was originally alive, usually in the form of some other plant. Chipped bark from trees, straw or hay from grain plants, even shredded newspaper that was originally some plant material, are all commonly used to keep these more tender species growing well.

These organics perform the same functions as the rock mulches I just described, and do even more. In addition to moderating soil moisture and temperature, these organics can actually enrich the soil as they break down. This is not very good for desert plants, but roses and fruit trees appreciate it. Heat and light do not bounce back from their surface, so the atmosphere just above is not particularly hot, a great bonus for plants that prefer a slightly cooler environment.

Gardeners can determine which kind of mulch is best for their landscape. Shredded newspaper would probably not be an attractive addition to the front of the house, but it could be very handy over a vegetable garden.

Whatever the choice – rock, bark or straw – mulch will help desert and non-desert plants alike to withstand our hot dry conditions.

Angela O’Callaghan is the area specialist in social horticulture for the University of Nevada Cooperative Extension. She can be reached c/o the Home News, 2275 Corporate Circle, Suite 300, Henderson, NV 89074, or [email protected].