|Weekly Express-News Article
“San Antonio Life”
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, May 26, 2007
“Fading or Yellow Lawns”
This is a transition time for our lawns. The most noticeable
thing is that some lawns are changing color as we proceed into
warm weather. If you are experiencing the color change, do not
panic, there are reasonable explanations and actions you can take.
The first instance of color change is being experienced in lawns
in the shade where the cool weather grasses grew and looked great
this winter. Rescue grass, annual blue grass, and rye grass reseed
themselves each year in some lawns in the shade. If you keep them
mowed they look great until the hot weather arrives. Now the cool
weather grasses are declining quickly as summer approaches.
Action Required – There really is no need for a special
response to this color change. The St. Augustine grass under the
weed grasses is responding to the rainfall and good growing conditions.
As the weed grasses decline the St. Augustine will fill the gap.
You can apply a slow release lawn fertilizer to help the St. Augustine
along, but do not panic by adding unreasonable amounts of water.
Keep the lawn mowed.
The second example of discoloration is due to iron chlorosis.
Recognize it by the parallel stripes of yellow and green on the
grass blade. This color change can be addressed by adding iron.
We have large amounts of iron in our soil, but it is locked up
in compounds with phosphorous and other materials characteristic
of our alkaline soil. Many lawns will grow through the chlorosis
as the soils warm up. Severe iron chlorosis, however, will weaken
Action Required - To correct iron chlorosis spray on an iron product
like Ferriplus or Iron Plus dissolved in water. A back pack sprayer
or even a hose end sprayer works well. For a longer lasting solution
mix one cup of iron sulphate (copperas) per bushel of compost
and spread it thinly over the lawn.