Forsythia and ornamental pears are in full bloom so it must be time to dust off the fertilizer spreader and fertilize your lawn to produce a lush, green yard. Right?

Wrong. Spring is not the best time to fertilize grass for a number of reasons.

"Fertilizing your lawn in the spring encourages weeds and reduces its drought tolerance. October through December is the best time to fertilize the lawn," said A. J. Powell, Extension turf specialist for the University of Kentucky College of Agriculture.

Spring fertilization encourages rapid growth of weeds such as crabgrass, chickweed and henbit. It makes grass more susceptible to leaf spot and some warm weather patch diseases.

Fertilizing your lawn in the spring reduces its tolerance to drought. Since all the grass growth is concentrated at the top, the root system stops growing. Grass with a poor root system cannot take up as much water and minerals. And this makes it less drought tolerant.

Although mid-April is not the right time to fertilize grass, it is a good time to apply broadleaf weed and pre-emergence crabgrass herbicides, according to Powell.

For effective control, apply the herbicide when broadleaf weeds are actively growing so the leaves will absorb the herbicide and move it into the plant. Use a liquid-applied material to cover weeds thoroughly. Apply the herbicide before temperatures become too hot, say above 85 degrees, to lower the chance of herbicide damage to grass and other plants. Spray when the wind is not blowing. Early morning is usually best time to spray.

"Use a pre-emergence herbicide to control crabgrass," Powell said. "We usually

recommend a pre-emergence herbicide application before mid-April. An exception is when the crabgrass hasn't germinated and your lawn has a history of problems with this weed. In this situation, apply a pre-emergence herbicide as soon as possible. Most of your crabgrass might not germinate until early June, especially if you have a good grass cover. A granular product is usually more effective than a liquid for pre-emergence crabgrass control."

When applying fertilizer or pest control product, be sure to avoid hard surfaces like sidewalks and driveways because rainwater can move product materials into storm sewers and eventually to rivers or streams that are sources of drinking water.

"Spring isn't an appropriate time to control turf insects either," Powell said. "White grubs, which make up 99 percent of our lawn insect problems, harm grass during the fall.

"Be sure you have a grub problem before using an insecticide. Look for brown patches in the lawn during September and October. Since white grubs eat roots, you should be able to pull up grass like a piece of carpet. The grass will have white grubs or loose soil beneath it. If you discover a white grub problem this fall, treat the lawn with a product like Dylox and water it in immediately.

"If your lawn does have a history of white grub problems, you can apply Merit or Mach II during June or July. These environmentally friendly insecticides remain active in the soil for a long time. Use Merit or Mach II only if your lawn has perennial grub problems."

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