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Index : Watering
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- 22. Conserving Water in the Landscape - Top
- I know it's hard to imagine that soon garden and landscape plants will once again be
thirsting for water. With all the rain and cool temperatures El Nino has provided, the
memory of our normal heat and drought is a distant one. But El Nino is quickly leaving;
and it won't be long before the ice on the Rillito River once again breaks. So now is a
good time to begin adjusting you watering schedule and irrigation system to accomodate
our plants and conserve water this summer.
Check your irrigation system. Are you watering your plants enough? Even well
established trees and shrubs will probably need a weekly soaking. Desert plants can
survive on much less, but will look better with an occasional watering. If plant leaves turn
a dull green, and begin to go limp or curl, they need water. Don't wait to give them a
good soaking. Plants that go to long without water reach what's called the permanent
wilting point'. This is the point of no return, when plants do not recover, no matter how
much water you give them. Don't waste water on lost causes. If you irrigate wilting plants
in the evening and they have not recovered by the morning, they're not saveable. Take
them out and replace them with drought tolerant varieties.
Check to make sure your irrigation system is putting out water where you need it. Drip
emitters can become clogged and tubes are often chewed by desert critters. If you
replace emitters, make sure they have the same gallonage output as others on the line.
Replacing a one gallon per hour drip emitter with a 2 gallon emitter will result in
insufficient watering. Replacing a one gallon emitter with a 2 gallon emitter will waste
water.
Deep water your plants. Water to a depth of 12 inches for small plants like flowers,
vegetables, herbs, lawns, and ground cover plants. For trees and shrubs water down two
to three feet deep to accommodate their propensity for deeper rooting. Deep watering
wets the entire root zone, and gives plants a greater reservoir of water to draw from.
After watering, check the depth of wetting by pushing a long screw driver or metal rod
into the soil. Concrete reinforcing rods work well for this purpose and can be purchased
precut at building supply stores.
Use the probe after watering by pushing it down as far as you can into the soil. Then pull
it out and measure how deep it went in. This it the depth of your watering. If you need to
increase watering depth, increase the watering time. For example, if your irrigation is set
to run for 1 hour, increase it to 11/2 hours, and recheck the depth of wetting.
Mulch the soil. This is a great way to conserve water. Organic mulch such as forest
mulch or desert mulch (produced locally) is best. A three inch layer of organic mulche
placed over the soil around plants helps hold in moisture and keeps the soil cooler.
Organic mulches have the added benefit of decomposing and adding organic matter to
the soil. As organic mulches break down, remember to add a fresh layer every year.
Organic mulches are also attractive and blend well with the native desert landscape.
Don't over-fertilize. Over fertilization promotes excessive leafy growth. This excessive
growth in turn, requires more water. Chemical fertilizers contain salts that can be damage
plants in hot, dry weather. These salts in the soil can draw moisture away from, and even
out of plants. If you must fertilize, do so sparingly. Organic fertilizers, such as milorganite
or composted manures, are good to use during the summer. They release their nutrients
slowly, and are less likely to damage plants.
Use desert adapted plants. When planning additions to your landscape, choose low
water use plants. You can't go wrong with the many beautiful native plants available at
area garden centers and nurseries. They also sell a variety of desert adapted plants that
come from other arid and semi-arid regions of the world.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona
626-5161.
Material originally appeared in Arizona Daily Star gardening column, on April 19, 1998. - Updated: February 21, 2001
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