December 1997 - Volume IV, Issue 12

Winter Sod - What, When, Why and How

David M. Kopec, Extension Turfgrass Specialist

In the dead of winter in the low elevation deserts, even the overseeded lawns are growing slowly. Staunch turf advocates who want a lawn or commercial sites requiring one, have a easy option for establishing a lawn in the dead of winter. The answer is "overseeded sod".

Overseeded sod is precisely what the name implies. It's bermudagrass sod that has been overseeded with perennial ryegrass already at the sod farm. When the grass is installed, the green surface is from the ryegrass -- the bermudagrass is 'underneath'!

The same procedures are used to prepare the soil for installing overseeded sod as you would do for any other sod. Note: In this case the ryegrass component of the sod does not have underground rhizomes, or above ground runners (stolons). Each plant is a collection of tillers which emerge as a "bunch" or clump from the sod. Make sure the overseeded sod looks even at the surface. Blotchy looking ryegrass (which is uneven) will not grow in appropriately if it is missing or damaged. You may need to sprinkle some seed on the top of any damaged pieces. Before laying the sod, irrigate the soil 2-3 days before the installation. The finished surface should not be "blanket smooth" or glazed over. Rather, a soft soil in the top inch with some "crumbly soil" left is best for the ryegrass roots to grow into. Water the sod with ½" of water directly after installation.

If the temperatures are cold, you may need to only water the lawn once every 3-5 days. Watch the turf closely. Wilted leaves mean that the soil is dry and/or the roots are not penetrating into the real soil. The turf should take about ten days to root. It will root more slowly than bermudagrass sod does in the summer. The grass should be cut when it reaches 35% over the "delivered" mow height. Or, ir you want to increase the height, let the grass grow up to the new height and mow it at the new height. Do this as a one time event. Then, mow the grass when it is 35% over the new elevated height (as normal).

With a restricted root system the ryegrass may develop three nutrient deficiencies in the cold soil. These include nitrogen, iron and phosphorous deficiencies.

Nitrogen deficiencies appear as light colored turf, with the lower (older leaves) turning yellow and then tan. Apply a nitrate containing fertilizer in the winter. Easy use products include ammonium nitrate (34-0-0) or potassium nitrate (14-0-45). Apply these when needed at the rate of ½ lb. of actual -N-/1000 ft2 once every three weeks. Iron deficiencies occur in wet cold soil and cause the upper leaves (youngest leaves) to turn yellow, and in some cases, white at the tip. To correct this condition, spray either ferrous sulphate, or better yet, an iron chelate product at 2-3 ounces per 1000 ft2 of lawn. Spray the lawn at 10:30 a.m. and let the iron sit on the leaves. Phosphorous deficiencies feature a stunted lawn, with purple colored leaves, usually on the underside of the leaf. Apply 0-27-0 (superphosphate) at the rate of 1 ½ lbs. of -P- (7 lbs. of product) per 1000 ft2 and water in. It may take two weeks for the purple color to go away.

The arrival of early summer means bermuda time. Unfortunately, the bermudagrass in the sod is often slow to emerge and the ryegrass may last longer than expected. That's because the underlying bermudagrass grows back primarily from new stolons which emerge from the crown and any of the underground rhizomes which were included in the cut sod. Tifway 419 has lots more stolons and shallow rhizomes compared to E-Z Turf Midiron. E-Z Turf Midiron has a lower stolon density and deeper and coarser rhizomes. The regrowth of bermudagrass is just slow the first year. Be patient! Do not shut off the water to kill the ryegrass. You will injure the bermudagrass. Instead, try scalping the ryegrass once and then fertilize the lawn each week starting June 1 with 1/4 lb. of -N- from a nitrate fertilizer. If it takes beyond August 15 to get the bermudagrass back to 90%, then you should seriously consider not overseeding the next year and let the bermudagrass rest.

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Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

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