Consider Lawn "Renovation" for Drought Damaged Grass

These grasses perform best in cool spring and fall weather, generally going dormant during the heat of summer unless they are watered on a regular basis when we are not receiving adequate rainfall. Turf-type tall fescue is the most drought-tolerant of the cool season grasses.

Mid-September to mid-October is an ideal time to start new lawns from scratch, and to renovate and overseed existing lawns. The weather is typically cooler, which is less stressful to grass seedlings, and we usually have decent moisture. Also, soil temperatures are warm, which will encourage good germination and root growth. Best of all, weed pressure is much less with a fall seeding than a spring seeding. While there are some winter annual weeds that germinate in fall, the vast majority of weed seeds germinate in spring.

Renovation of drought-damaged lawns should start with a soil test to ensure that soil pH and nutrients are optimum to support a healthy lawn. If broadleaf weeds have taken advantage in areas where the grass has thinned out, apply broadleaf weed killer for lawns to get them under control. The area can be reseeded two weeks after applying broadleaf weed control. The weeds should remain undisturbed for seven to ten days to allow the herbicide time to work.

The next step is to cut the grass fairly short, around three-quarters of an inch (which is much shorter than the two-and-a-half to three inches recommended for regular maintenance). Bag the clippings or rake the area well to remove all debris.

Next, check the thatch layer, which is a layer of partially decomposed grass stems and roots that develops between the top growth and the soil surface. A little thatch acts like mulch in that it helps conserve soil moisture and moderates soil temperatures. Over one-half inch of thatch becomes problematic in that it becomes water repellent once it dries out completely, making the effects of a hot, dry summer even worse for the grass. It builds up over time and must be mechanically removed periodically. If you do not have a soil probe, dig a small hole in the lawn, then take a complete slice from one side of the hole – thatch is evident as a layer of organic matter between the growing grass and the soil surface. While a small area can be de-thatched by hand, it is more practical to rent a power de-thatcher for larger areas. Dethatching is very stressful for lawns and should only be done in late summer or early fall. Dethatching will expose sufficient soil to use as a seedbed for the new grass seed.

If the lawn does not need to be dethatched, another tool to bring up soil for a seedbed is the core aerator. This piece of equipment pulls three- to four-inch cores of soil out of the ground and deposits them on the soil surface. Core aeration helps break up compacted soil, which allows increased rooting and better infiltration of water.

Once you have run the de-thatcher or aerator, apply limestone and fertilizer as recommended by your soil test results. Then drag a section of chain link fence over the area to work in the amendments and to break up soil cores. Small areas can be worked with a rake.

Now it is time to apply the grass seed. When you are applying grass seed with a lawn spreader, divide the seed into two equal parts. Apply one part in one direction and the other in the perpendicular direction to ensure even coverage. Drag or rake the area again to work the seed into the soil, and then use a lawn roller to firm the seed into the soil.

In areas where there is little or no existing grass, mulch with a thin layer of clean oat straw to help maintain soil moisture and protect the grass seed. Do not apply such a thick layer that you will have to remove it when the seed starts to germinate. In areas where there is a decent stand of existing grass, the grass will act as the mulch.

Water the seeded area shallowly and frequently – it is important not to let the seed dry out once it starts to germinate. As the grass starts to grow, water more deeply and less frequently. And once it gets tall enough to cut, do not be afraid to mow it.

For more information on lawn renovation, visit Penn State’s College of Agricultural Sciences publications website at:  http://pubs.cas.psu.edu/PubSubject.asp?varSubject=Lawn%20and%20Turf

Scroll down to “Renovation of Lawns.” Another publication that may be helpful is “Turfgrass Species for Pennsylvania,” to help make sure you choose the appropriate varieties for the conditions in your yard.

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