Teague: Mulch is key to keeping weeds out, moisture in

FresnoFebruary 28, 2014 

This too warm/too early spring weather has brought on a sudden explosion in the weed population, even with little rainfall. A quick tour of your garden or your neighbors' should provide good evidence of just how important mulch is in preventing weed growth. It's easy to see that unmulched planting beds and bare dirt patches are rapidly filling with water-stealing weeds, but areas that have been covered with at least 2 to 3 inches of mulch are nearly weed-free.

Two other really good reasons to spend time and money laying down mulch in your garden will become really obvious as this drought continues into the hot summer months.

It's estimated that a 2-to-3-inch layer of mulch can reduce water consumption by plants by 30%. The mulch slows evaporation and also reduces and regulates soil temperature, preventing temperature fluctuations that can stress plants. And, boy, will our drought-stricken plants be stressed this summer!

The other good reason to mulch all planting beds and bare dirt areas in your garden this year is to prevent dust from blowing onto plants. We haven't yet had too many heavy rainstorms this season to soak the soil and wash down dust. Much of the foliage in our landscapes is still covered with last year's dust. Dust clogs breathing pores on leaves, limiting their intake of polluted air and exhalation of cleaner oxygen. We can live with dusty patios and driveways, but trees and bushes can die if leaves are coated with dust and we won't have extra water to wash down driveways or plants this year. Covering bare, nonirrigated dirt areas with mulch as well as raking up leaves and debris on lawns and hardscapes instead of using leaf blowers will help keep some of the dust off our plants and out of our air and lungs.

Some trees such as redwoods and pine trees drop a lot of debris; that debris can be left under the trees to act as mulch if the trees have shown no signs of disease or insect infestations. The garden won't be immaculate, but after all, the debris is nature's way of conserving water and protecting the root systems of these trees.

Cedar bark mulches are hard to rake and the bark strands also weave together to form a water-resistant mat. Cocoa hull mulches are toxic to dogs. Chip mulches will do a better job of retaining moisture than fine textured humus or compost products like redwood compost, mushroom compost or nitrohumus (all of which also are used as soil amendments) and the heavier weight of the chips makes them more difficult to rake away.

In our climate, with extreme summer heat, a 3-to-4-inch layer of mulch is recommended to conserve water and moderate soil temperatures. When laying down mulch, keep it a few inches away from trunks and stems. Wet trunks and stems can rot.


Elinor Teague is a Fresno County master gardener. Send her plant questions at etgrow@comcast.net or features@fresnobee.com ("plants" in the subject line).

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