The issue this spring seems to be the light green color of our lawn grass. In most cases it is accompanied by fast growth. The cause of the light green color is a deficit of nitrogen and/or iron.

The deficit exists for several reasons. The bountiful rains have kicked the grass into a high growth mode. Growth is so fast that the plant is not able to pull up enough nitrogen and/ or iron from the soil to fully  meet the need. The roots uptake enough to minimally support the high growth rate, but not enough to  produce a rich green color.

The grass will reach an equilibrium point as the rains slow, the roots expand and time passes. Unfortunately it may not be at the high growth rate and dark green color you desire.

One option is to give the lawn a special fertilizer application. An application of slow release lawn fertilizer such as 19-5-9 will bring nitrogen levels up high enough to take advantage of the generous rains and maintain the growth rate.

Slow release lawn fertilizer is a happy combination of slow and fast nitrogen sources. Fifty per cent of the nitrogen will be available for immediate use by the lawn and 50 per cent is released over 3 months.

There is another product available on the market, “Iron Plus” that is both a source of fast release nitrogen and has a high level of iron.  Use it instead of slow release lawn fertilizer if the the yellowing is expressed as straight lines of yellow on the grass blade instead of a uniform yellow.  The yellow lines indicate that the main nutrient shortage causing the yellowing is  iron.

Some homeowners prefer to use organic fertilizers. They are good as a long term nitrogen  source but do not release the nitrogen fast enough to address the current nutrient gap.

On mowing, remember that each lawn grass has a mowing height that is best suited for its growth characteristics. Mow St Augustine at 3 inches or taller, zoysia grass at 2 inches, and Bermuda grass at1.5 inches or less.  Mow frequently enough that no more than one-third of the blade is removed at each mowing. In our current weather situation (rain and mild temperatures) that may mean mowing twice per week.

Dr. Calvin Finch is Urban Water Program Director for the Texas A&M Institute of Renewable Natural Resources.You can ask Calvin question and hear his answers on the air as he co-hosts the Gardening South Texas on the air at KLUP (AM 930) Saturday and Sunday from 12:00 to 2:00pm.