A Question of Roots
May 2009 | Linda Chisari, Crest

Photo: Linda Chisari

Are you thinking of tearing out your existing plantings and replacing them with drought-tolerant varieties? Don’t! Many of the established trees and shrubs we planted long ago are drought-tolerant, thanks to well-established root systems. The ubiquitous India Hawthorne, Mock Orange, Junipers and even Camellia, just to name a few, all need little supplemental water, once they are mature-probably much less than we are giving them

What’s needed may be less drastic than pulling out grass. Photo: Piper Underwood.

The first step for those of us with mature gardens is to re-evaluate our current watering schedules and gradually cut back to fewer waterings per week. While soil characteristics, plant type and topography all influence water needs, a few general rules apply. If you have been watering 3 or 4 times weekly, try cutting back to 2 times weekly then, if no ill effects are seen, once weekly or even once every other week. Do not reduce the duration of watering to less than about 15 minutes per session. Except in very sandy soils, water takes that long to penetrate the entire root zone. Less time encourages shallow-rooted plants that are unable to withstand long periods without water. You may see fewer flowers when water is restricted, but leaf turgor and luster should be maintained. If the leaves hang down, curl under or develop a dulled surface appearance, you may need to adapt less severe cutbacks. Consider purchasing a Moisture Meter. This simple tool allows you to insert a probe 8”-10” into the soil to assess soil moisture at that depth and determine whether additional water need be applied.

While you are re-assessing your irrigation schedule, examine the system, too, to make certain it is functioning with maximum efficiency. Clean heads and filters. Fix leaks. Redirect heads that are watering sidewalks. Remove heads that are no longer needed. Use newer heads that put out fewer gallons per minute. Be sure your plants have basins that trap the water and direct it to its roots.

Drought tolerant bouquet of Yarrow, Shasta Daisy, Stokes Aster, Mexican Sage, Mexican Evening Primrose.  Photo: Linda Chisari.

Next, keep a 2”-3” layer of mulch under your plantings to reduce the amount of moisture lost to evaporation and to keep the soil surface cool. An added bonus will be fewer weeds and weeds use water, too! Mulch must be replaced at least annually as it breaks down and works its way into the soil. Redwood bark is most often used but other conifer products, peat moss, plastic, newspaper and your own shredded yard clippings work too. Agriservices, Oceanside, and Miramar Wholesale Nursery, San Diego, both sell excellent mulch made from recycled garden waste.

Adapt a schedule of less-frequent fertilization to slow down plant growth and reduce the need for water. Semi-annual fertilization with a balanced product should keep plants healthy without stimulating excessive top growth.

Photo: Linda Chisari.

Plant annuals and other water-loving plants in containers. When annuals are mixed in with deeper-rooted shrubs and trees, all plants must be watered according to the needs of the shallow-rooted annuals. Consider reducing lawn area to a size that is required for a children’s play area or other specific recreational needs. Keep this lawn de-thatched and aerated so that the water you apply can penetrate and encourage a deeper root system. Educate yourself about drought-tolerant plants so that future additions to your garden use only as much water as is appropriate in our desert climate.

Finally, remember that Fall, not Spring, is the ideal time for planting in our Mediterranean climate. By planting when days are shorter and cooler, plants are encouraged to put their energy into root growth that can support the rapid top growth stimulated by the warmer, longer days of Spring and Summer.

Visit Linda Chisari's website at: www.lindachisari.com