Extra rain means extra care needed for lawns

July 24, 2013 

It may be sunny outside but the effects of the rain may still be with us, especially in lawns. The current and future health of our lawns is influenced by the excess rains we have experienced. Keep this in mind when managing lawns from now through next spring.

Lawns are not a large green carpet. They are a living collection of plants which must be cared for. The recent rains may have stressed some of these plants even if it does not show right now. We need to carefully manage these stressed lawn plants to help them recover so that they will be strong enough to grow into the fall and to green up next spring.

One effect of excess rain is waterlogged roots. Roots need water (and we are thankful for the rains) but they also need oxygen. Waterlogged soils contain little of the oxygen needed by plant roots. This is especially a problem on clay soils, compacted soils or in low areas where water collects.

To manage waterlogged soils, do not mow or fertilize wet areas until they dry. Once the soil dries well, fertilize lightly using a complete fertilizer (see details below). Keep heavy equipment out of the area because it is easy to compact wet soils.

Excess rain can leach fertilizer -- wash it from the soil where the plant cannot reach it. You may need to fertilize the lawn again once the soil is dry. Apply a complete fertilizer, one that contains nitrogen, phosphorus and potassium. The fertilizer label will tell you the contents of the fertilizer.

The numbers on the front of the bag tell the fertilizer content. The first number is the nitrogen percentage, the second is the phosphorus and the third is the potassium. So a 5-10-15 fertilizer contains 5 percent nitrogen, 10 percent phosphate (phosphorus) and 15 percent potash (potassium.) Select a fertilizer containing all three. Look for a fertilizer with a relatively high potassium level (the last number). For now, avoid fertilizers with a lot of nitrogen but little potassium.

Use rates listed on the label but half these when fertilizing centipede grass. Use slow-release fertilizers on St. Augustine grass. You can use slow release fertilizers on any lawn type, if you like.

Finish the last lawn fertilization no later than Sept. 15 (Sept. 1 for centipede). If you use a lawn care company, it might fertilize later than this which is often OK because they use different rates and types of fertilizer.

The reason for applying extra potassium is that potassium leaches rapidly from the soil. It is also important in maintaining the disease and cold weather resistance of the plant. Our lawns will soon be dealing with one of the most stressful times of the year: the fall-winter transition. Potassium helps lawns go through the winter healthy and strong.

Wet soils also encourage diseases, so if you have had problems with Take All Root Rot or Brown Patch in the past, a fungicide application in September and again in October might be a good idea this year.

Weeds did not mind the extra rainfall. The weeds in my lawn seem to be quite happy now. I have a light green patch of healthy grass next to our walk. It looks great, but I know it is actually crabgrass. It will look good until the fall when it will die leaving a bare patch where turf should be and a bunch of seeds for next year’s crop of crabgrass.

Careful lawn weed control now should reduce weed pressure, encourage late season lawn growth and reduce bare patches next spring. The best weed control is to identify the weed and the lawn grass and then purchase a herbicide that will kill this weed. On the other hand, there are some general weed controls that will kill many (but not all) weeds.

If you have broadleaf weeds, use herbicides containing 2,4-D and dicamba. For crabgrass, select a herbicide containing quinclorac. Quinclorac is relatively new to the home market, so you might need to call or visit around to find it. Read and follow all label directions when using a herbicide or other pesticide. Not all herbicides can be used on all lawn types.

Willie Chance works with the University of Georgia Center for Urban Agriculture and helps to train the turf and landscape industry.

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