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Time to put away the nitrogen
Lawn and garden
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This year has been a curious one. We jumped right from winter into summer and skipped spring altogether.
In the last two weeks we went from oppressively hot and humid with heat pumps working overtime to upper 40-degree lows and windows wide open for some excellent sleeping weather. I can venture outside without a gallon of ice water to stay hydrated.
Folks are out rediscovering their lawns and landscapes. Why, I just can’t believe that jasmine grew that far since spring. And the loropedalum is downright shaggy. The bawl of mowers, line trimmers and edgers fills the weekend air.
But in your haste to put that lawn back in shape, there are a few things of which to be careful. The main one for today is: Put away the nitrogen!
Maybe it was just too hot to put down the fertilizer this summer. If you missed an application the lawn will probably forgive you. What it won’t forgive is you trying to make up for lost time by putting down fertilizer now. Yes, and that includes weed and feeds. Over fertilization and fertilizing your lawn at the wrong time causes more problems and costs more to fix than under fertilizing.  
For centipede lawns: no nitrogen before May or after August.
For St. Augustine lawns: no fertilizer before May or after September.
If you have not fertilized yet and your soil test indicates low potassium, you can apply straight potash or a nitrogen-free fertilizer now or later in the fall. Do not apply phosphorous (the middle number on a fertilizer analysis) to a centipede lawn. If pH adjustment is needed, appl y lime or sulfur as needed in autumn or winter as these treatments take months to change soil acidity. But please, no nitrogen!
The reasons behind the recommendations are based on turf biology. Here on the Georgia coast, our preferred lawn grasses are centipede and St Augustine. These are warm season grasses. They grow best when the weather is warm (duh). But during the cooler times of the year, these grasses go semi-dormant and grow very little.
Warm season grasses come out of dormancy when the soil temperature at 4-inch depth in spring warms up to and holds a minimum temperature of 65 degrees Fahrenheit. They go back into dormancy when the soil temperature at the 4-inch depth drops below 65 degrees in autumn.
On Sept. 26, 4-inch-depth soil temperature was 81 F and dropped to 71 F by Oct. 6. We are not far from dormancy if the cool weather continues.
Well, so what? This is what: Nitrogen is a highly sought-after element by all life forms. Turf is not the only thing living in your lawn. There are insects, fungi and lots of weed seeds just waiting for the chance to make their presence known, and often what keeps them off center stage is lack of nitrogen.
The rates and timing of fertilizer applications are based on giving enough for your turf to thrive while not putting on so much that we activate the insects, weeds and fungus. Your turf will be going dormant soon, but the insects, weed seeds and fungi are always active.
Fertilizing with nitrogen now will almost certainly ensure a surplus of nitrogen to kick off those winter weeds.
So don’t feed the enemy. As Forrest Gump would say, “One less thing.” Now you can get back to those Halloween decorations.

Gardner is the Bryan County Extension Agent for agriculture and natural resources. His column appears every other Wednesday in The News.
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