Mulch to Conserve Soil Moisture

By Kelly Feehan, Extension Educator

The long range forecast is for another dry winter. Last winter followed a summer of good moisture. This winter follows a season of exceptional drought.  I have been writing about fall and winter watering which can continue as needed and if feasible. If the forecast holds out and dry conditions continue, young trees and shrubs and all evergreens would benefit from irrigation about twice a month.

Preparing for a Dry Winter
Mulching plants and applying antitranspirant products to some plants are other practices to use to reduce injury from winter drying. Between irrigation, mulching, and antitranspirants, mulching may be the easiest to accomplish.

Mulch conserves soil moisture by reducing evaporation of water on sunny and windy winter days. Mulch helps prevent soil cracks from forming and exposing roots to cold temperatures and winter drying.

A common question last year was what to do about plants like spring flowering bulbs that begin to grow during winter. The long range forecast is for fairly average temperatures so we may not have as much of an issue with premature growth this winter.

Applying Mulch
Placing an 8 to 12 inch layer of coarse mulch over bulbs and other perennials can delay or prevent early growth. It also protects the crowns, growing points, of perennials and strawberries from winter drying and insulates the entire plant from temperature extremes. Something snow cover would normally do. Wait until soils are close freezing before covering plant with mulch.

While winter mulch is typically used on less hardy plants, it will benefit most plants in an open winter with little or no snow. With being in the midst of exceptional drought, consider mulching valuable landscape plants whether they are hardy or not.
For trees and shrubs, place a four inch layer of mulch in at least a four foot diameter ring. If the soil is dry, moisten it before applying mulch. Keep mulch one foot away from trunks and stems to avoid voles making a winter home in the mulch and gnawing on the wood.

If mulch or time is limited, evergreens and young plants should be first on the list to mulch. Next mulch established plants growing in south facing exposures or near pavement. If necessary, only place mulch on the south side of a tree or shrub. Once more mulch is available, mulch the entire plant.

Antitranspirant products are emulsions of wax, latex, or plastic that form thin films on plants to minimize water loss from plants. These products are not convenient to work with. They are typically recommended only during winter on valuable conifer and broadleaf evergreens growing in stressful sites.

If used, select the right product for the plant as there are toxicity issues. Read and apply these products according to label direction. If weather allows, they need to bet applied once every six weeks in late November or early December, early to mid-January, and mid to late February.

Avoid covering plants so much that they become sticky with needles glued together. Have warm, soapy water nearby to clean out the sprayer immediately or the sprayer can be ruined by the product.