Weekly Express-News Article
Saturday, March 11, 2006
By Calvin R. Finch, PhD, SAWS
Water Resources Director, and Horticulturist
 “A Special Irrigation Initiative is not Recommended”  

            After several years of cooperation and relative unity among horticulturists on the question of reducing water use on our landscapes, there are some cracks in the alliance.  Some horticulturists believe that the ten month period of drought we have experienced in 2005 and 2006 is a major threat to our landscapes and the answer is to irrigate with a vengeance to save our lawns and trees.  The problem with that strategy, of course, is that we will be irrigating our lawns at the same time as area farmers are irrigating their corn and other crops.  The net result will be that the aquifer will fall to 650 feet and drought restrictions will be imposed.

 

            I am on the side of the large numbers of plant people that are recommending moderation.  I believe your landscape will survive well and your investment will be protected best by following the usual pattern of irrigating St. Augustine grass once every three – four weeks until June (if we do not receive rain).  The strategy will also postpone aquifer drops and give us time to receive some rain.  If we begin watering every week now, at the same time as the farmers are irrigating their crops, we can expect to move into drought restrictions very quickly.

 

Here are my reasons for thinking moderation.

 

·      Most plants in our landscapes are well adapted to periods of drought.  If they are well established, they have capabilities to survive long, severe droughts.  Live oaks, Texas mountain laurel and even lawn grasses like zoysia, Bermuda and buffalo grass evolved in droughty climates.

·      We only had about 16 inches of rain in 2005, half our average for the last ten years, but we also had four wet years before last year.  The trees and shrubs have had a long period of “plenty” to store nutrients and prepare for stress.

 

·      Even last year, despite the lack of total rain, did not stress plants as much as expected.  It was a cool year and rains were relatively well timed.  Rains in July helped keep per capita water use at a very low rate of 130 gallons/person/day.  Landscape plantsprospered despite limited rains. 

 

·      It is true that some evergreen plants (including ligustrum, primrose, jasmine, and even oleanders) are showing stress due to drought, but that may be a result of lush growing conditions last spring and over the last four years.  Most plants, including these evergreens, will adjust to the conditions and survive. 

 

 

·      Anecdotal claims of plant death only become evidence of amajor threat when the numbers are actually measured and compared to other years.  Plants die every year in San Antonio.  We would expect more to die in extremely dry or extremely wet conditions.  So far, there is no real evidence that the drought stress is exceptionally devastating on plants this year, and more importantly, there is no evidence that a major irrigation initiative will reduce normal mortality rates. 

 

·      Dormant plants do not use very much water.  They are particularly capable of surviving a dry winter.  Check out the shadetrees and shrubs in your neighborhood.  Many are leafing out.  Do you see any major abnormalities?  The major stress will come later in the summer.  Save the irrigation water and your budget for them.

 

·      St. Augustine grass does not go dormant well, but it has some capability to survive stressful times due to drought or cold.  The results of the SIP research that was conducted over four years in the late 90’s indicated that the grass variety survived with water every two weeks in the hottest part of summer, surely it can survive with irrigation every three or four weeks in the winter time. 

 To discuss these issues further, attend the Spring Bloom Giveaway at the SAWS Headquarters Building (2800 U.S. Hwy. 281 North, Old Valero Headquarters), today from 9:00 a.m. – 1:00 p.m.  There will be landscaping lectures every half hour and a free blooming xeriscape plant (three-inch size) for the first 2,000 visitors 14 years or older.

 

SAWS’ Citizen’s Advisory Committee (CAP) meets next week.  The CAP reviews and monitors water resource projects.  The Chairman is Howard Peak.  It meets on March 14, 2006, at 6:00 p.m., at Tower II ofSAWS Headquarters (2800 U.S. Hwy. 281 North).  The main topic of discussion in March is the Brackish Groundwater Desal Project.  Call (210) 233-3670 for more information and directions.