Weekly Express-News Article

By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist

Saturday, May 17, 2008

 

“Watering Advice”

 

            With the arrival of hot weather it is necessary that gardeners be conscious of the water needs of their plants. The goal is to meet the needs of the plants without wasting water.

 

            Container plants will need to be watered at least once/week and probably twice per week, especially if the top is large in comparison to the container.  A larger container is a larger reservoir.  Apply enough water that the whole container is moistened and water begins to seep out the drainage hole.   

 

            Water most annual flowers and vegetables at the same frequency as you do containers.  Twice per week is often necessary to produce food or flowers.  Mulch the plants and use drip irrigation or a leaky hose for most efficiency.

 

            Water newly plant trees and shrubs every time the soil under the mulch dries the first summer.  Water generously at the base of the plant.  Drought-tolerant plants are slow to put their roots into a droughty soil.

 

            Most established trees and shrubs have much more drought capacity than the lawn grasses do.  A lawn may go dormant if it does not receive rain or irrigation at least every two weeks.  Trees and shrubs can retain their leaves in the midst of summer long droughts.  If you decide to water your trees or shrubs once/month in a droughty summer, water with a leaky hose or let the hose run on the drip line for a long enough time that water soaks in to six or eight inches.  A once/month soaking is especially desirable for blooming plants such as modern tough or old-fashioned roses.

 

            Most lawns require irrigation once/week to stay green.  If you have less than four inches of soil, you may have to run the sprinklers two times per week.  If your sprinkler is operated more than once/week, use less water for each application because the soil reservoir is smaller and it cannot store as much water. 

 

            Every sprinkler system is different and even the heads in a sprinkler system can be different.  For a relatively accurate measurement, place several pie plates on the yard and see how much water is applied in 15 minutes.  If the plates average one-half inch in the 15 minutes you will know that your sprinkler heads on the average, apply one inch of water in 30 minutes. 

 

            It works best in terms of efficiency if you change the amount of water you apply each week to your lawn based on the weather.  Each Saturday the Express-News prints the SIP report (usually page three of the San Antonio Life section) that uses the week’s weather to determine exactly how much water to apply. The other option is to sign up for a personalized SIP recommendation to be e-mailed to you once per week on the day you designate.  To enroll in SIP, visit the SAWS’ website at www.saws.org, click to Conservation and then to Seasonal Irrigation Program (SIP).  Many modern controllers can be set to apply .5, .75 or 1 inch of water (based on time), and then you just select which of the options to use that week based on the SIP advice.

 

            Every lawn has places where the soil is shallower than the rest of the yard, or where the soil is more severely compacted.  Sprinkler systems are also commonly applying different amounts of water from one spot to the next.  The result can be that you may have a few dry spots even when you follow the guidelines.  Green up those spots by hand-watering a little once per week.  The task is relaxing and is more efficient than watering the whole yard in order to apply more to a small dry spot. 

 

            If you are a SAWS customer, call (210) 704-7283 for a free sprinkler system audit.  The auditor will determine if you have any leaks, look for poorly performing sprinkler heads, and check the settings on your controller.

 

            If you have a sprinkler system, have your irrigation company service the system now and every six months.  They should adjust heads and fix any leaks.