Mulch

When we think about gardening, admittedly, mulch isn’t the fun part, the part that you just can’t wait to dig into come spring. But mulch is worth giving some thought to and there are lots of reasons why. Not thinking about mulch, for instance, could easily lead you to make the dreadful mistake of picking any old thing like, say, gravel or decorative rock — possibly even white rock —which, as I may have ranted about before, is definitely the most hideous mulch imaginable.

Rock not only makes an ugly, completely unnatural-looking mulch, it also creates an inhospitable environment for plants since it’s usually spread on top of a sheet of black plastic. The plastic is there to keep the weeds out, but it also ensures that water and air don’t reach the soil so you can say goodbye to earthworms and all of the microorganisms that help keep soil healthy. Even if more porous fabric is used, it doesn’t solve the problems caused by all those rocks heating up in the hot sun and baking the plants and surrounding soil. 



The purpose of mulch is to do things like suppress weeds by covering the soil surface, conserve water by helping retain soil moisture, moderate soil temperature (particularly in winter) and minimize erosion. One of the most attractive and effective mulch choices out there (in my opinion) is shredded hardwood. Dark and earthy smelling, shredded hardwood can be used around trees and shrubs, as well as throughout perennial garden beds.

Spread mulch to a depth of 3 to 4 inches for best effect; but if you don’t like a look that thick, a couple of inches will do. Because the mulch will break down over time, you’ll need to reapply it every three years or so. I like to have mulch delivered to my driveway so I can load it into a wheelbarrow and haul it around from there over a weekend. But if you’re fine with making multiple trips, you can also pick up individual bags of mulch at any garden center and bring them home. One more thing: if you haven’t heard about this yet, gardeners are being urged to say no to cypress mulch because the aggressive harvesting of cypress trees is not only causing the trees’ disappearance, it is decimating the natural protective barrier from hurricane winds and rising waters cypress trees provide in places like Louisiana.

For those who don’t like the look of wood mulch, and I know lots of gardeners who don’t, it’s fine to use a thick layer of compost as a top dressing. Like wood mulch, compost should be spread to allow about 2 to 3 inches between it and the plants it surrounds. While gardeners gain a clean, natural aesthetic with this approach, you lose some advantages, most notably a weed barrier. Maybe because it looks like compost or soil, at least, lots of gardeners make the mistake of thinking that sphagnum peat moss is a mulch. Peat moss is mostly used as a soil amendment, though in truth it makes a poor one when used anywhere but in containers.

The problem with peat moss is that, like cypress, when we buy it we are harming the environment, so we really should stop using it now. Peat moss is mined from bogs that provide habitat for all kinds of plants and animals. As wetlands, these bogs help prevent flood damage and they purify the air. Once destroyed, it can take hundreds to thousands of years to reestablish. Despite assertions by the horticulture industry that peat is not mined at a rate that outstrips its growth, environmentalists and conservationists doubt and disagree with those claims. So gardeners will have to decide for themselves what the best choice is on this one.

Of course there are lots of other types of organic mulch out there: grass clippings, pine needles, leaves, straw, sawdust and newspapers. But all of these have their drawbacks, not the least of which being that most of them are pretty unpleasant to look at. Cocoa bean hulls are a popular organic mulch choice, though. Having tried them several years ago, I can tell you this story.

Minutes after spreading them around my whole garden smelled like hot chocolate. It was wonderful; but it lasted only a few days and then I was left with a sickly sour aroma, and then the mulch got all matted down and moldy until finally, thank heavens, it decomposed into nothing and went away. And though claims of cocoa bean mulch being toxic to dogs seem to have been overly exaggerated, it does seem as though there is come lingering concern over it being a choking hazard and causing animals at least some gastrointestinal distress. Oh, and did I mention that it was really expensive? See? I told you there is much to learn about mulch.

This post originally appeared in the Southwest Journal.