Q: I want to help my Bermuda lawn to come out of dormancy and replace my overseeded ryegrass. I’ve heard that scalping the winter grass and/or withholding water will encourage and speed up the transition back to Bermuda. What are your thoughts on this?
A: Either of these will have a drastic effect on the appearance of the lawn, causing the look of an uneven or forced transition. In the old days, you could scalp ryegrass in the late spring, and the stress would severely weaken the ryegrass. The Karsten Turfgrass Research Facility tested the scalping techniques coupled with different nitrogen fertilization applications in order to “force” the transition back to Bermuda grass. Over the last several years, many ryegrasses have had better heat tolerance than previous varieties. They last longer in the early summer and tolerate close mowing and scalping to some extent. Note that if you scalp, you will scalp the underlying Bermuda grass as well. This occurs more on common Bermuda grass than Tifway or Santa Ana. If you scalp, do it for two to three mowings, then mow as normal for the Bermuda grass.
Shutting off the water will injure the ryegrass, but also drastically slows the new Bermuda grass underneath.
All winter and spring, the Bermuda has been kept wet, even though it has been sleeping. Therefore, the Bermuda grass is not drought-hardy, compared with unwatered and non-overseeded Bermuda grass. The sudden drying out of the Bermuda grass will slow its growth, and thus produce a slow transition.
The ryegrass eventually becomes less competitive when the weather becomes more humid and the high nighttime temperatures occur. This is usually during the mid-July monsoon. At this point, the ryegrass is using up food reserves day and night. The end is near for the ryegrass.
In May, apply 1/4 to 3/8 pound per 1,000 feet of actual nitrogen per square foot of lawn. The product can either be an N-only source (21-0-0, ammonium sulfate) or come from a complete fertilizer that has N-P-K. Examples include 10-6-4, 21-7-14, 20-10-10, etc. The product can also contain iron and/or sulfur.
Get more plant tips and tricks on John Chapman's Southwest Gardening Web site.