Timing is key to lawn

My dogs are gross.

I love them and I'd bawl if something happened to them, but I'm here to tell you they are gross.

They lick things they shouldn't be licking, eat things not meant to be eaten. Occasionally, we find socks in the backyard twisted like they've been run through a tubular trash compactor. Once, we found underwear. I swear. Our trash cans have lids because a used Kleenex is like cotton candy. Dental floss, Q-tips, wrappers and things I can't even mention have been plucked from the bathroom trash.

If they were stray dogs living off the land, I'd get it. Food is food. But there's a time and a place for everything. The same applies to fertilizing lawns: There's a time and a place.

For instance, now is not the time to fertilize with nitrogen in the Lowcountry. Resist the bags of winterizing fertilizer that contain nitrogen. August is the last month we should fertilize with nitrogen. That type of winterization is formulated for cool-season grass growing north of the Mason-Dixon Line. Lawns such as Kentucky bluegrass go semi-dormant in winter and use an early November application of nitrogen, as opposed to our warm-season grasses, such as centipede, that go mostly dormant and need to harden off for the winter.

When fertilized, plants consume carbohydrates and grow. Carbohydrates, simply put, are food, the end product of photosynthesis. Late nitrogen will deplete the carbohydrates that the turf is attempting to store for the winter because photosynthesis, thus carbohydrate production, slows in the fall.

In the spring, when new growth is emerging, turf has to draw from these carbohydrate reserves to re-establish the lawn because there is a limited amount of green, photosynthesizing tissue. However, late nitrogen applications can leave these reserves critically low. This doesn't automatically kill the turf but predisposes it to stress, disease and insects.

Another issue with late nitrogen is succulent growth. Low temperatures damage the cells that make up foliage. Older foliage is more tolerant of temperature stress. As temperatures decrease in fall, old growth prepares for winter. However, new growth has thinner cell walls and is much less tolerant and is completely unprepared.

New growth is also more susceptible to disease because fungal spores can easily penetrate the thin, waxy cuticle that covers a leaf. Research has shown the incidence of brown patch disease, which centipede and St. Augustine are susceptible to in spring and fall, increases with nitrogen availability. Brown patch severity and frequency can be reduced with less nitrogen, or at the very least the proper timing.

I have St. Augustine grass in my front lawn, and the growing conditions are conducive to brown patch: shady and damp. However, I mow it at 3 1/2 to increase photosynthetic tissue. I also put down a light nitrogen application in May only, avoiding any chance of available nitrogen in September, when the disease is most active. I probably could put down another application in August, but why mess up a good thing. So far, there has been very little disease.

If you want to fertilize now, use potassium. It will not affect the color or growth but will boost the turf's ability to tolerate temperature and drought stress. If you want a darker green color, try an application of iron. I haven't had very good results with granular iron but have found liquid applications to be effective. Just make sure the product is evenly applied to avoid striping.

It's advisable to do a soil test to analyze nutrient status and availability. Potassium is frequently low in our sandy soils, and iron can be tied up in soils with a high pH. Go to Clemson's Web site for soil test information: www.clemson.edu/agsrvlb.

It's hard to resist a cute dog and a lick on the cheek. Just keep in mind where that tongue has been.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony.bertauski@tridenttech.edu.