Avoid Fertilizing Lawns in Early Spring - U of I Extension

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Avoid Fertilizing Lawns in Early Spring

This article was originally published on March 1, 2007 and expired on March 23, 2007. It is provided here for archival purposes and may contain dated information.

Fertilizing lawns may not be the best for the grass in the long run, according to David Robson, University of Illinois Extension horticulture educator. But with all the advertising and chemical combination products available in the spring, it is almost impossible not to apply some form of plant food.

"The primary purpose of spring lawn care is to produce a lawn tough enough to survive the summer," says Robson. "The ideal lawn care period starts September 1 when temperatures are on the slow decline."

Studies at the University of Illinois indicate grass roots are actively growing when temperatures are between 55 and 65 degrees. Grass shoots start developing when temperatures are between 60 and 75 degrees.

Grass roots are the first to start thriving when spring temperatures warm. New and deeper roots are formed, creating a network of interlocking roots. The deeper the roots, the more likely the grass plant will be able to survive hot, dry summer conditions.

"Unfortunately, nitrogen fertilizer promotes shoot growth at the expense of the root system," says Robson. "Even with cool soil temperatures, the grass plant shifts growth to shoots to use the nitrogen. The root system stays undeveloped. We have been conditioned to expect a thick, green, lush lawn in the spring as soon as temperatures warm. Part of the problem can be traced back to the crabgrass killer combination products."

Pre-emergence weed killers must be applied before the weed emerges. Since crabgrass germinates by mid-April, most chemical applications are applied by the first of April. And because most crabgrass pre-emergence weed killers contain fertilizer to help "green up" the lawn, we get shoot growth instead of root growth.

This spring, search for a crabgrass or pre-emergence weed killer that does not contain fertilizer. These products may be more difficult to find, but they are available. Check with local garden centers, greenhouses or nurseries.

If you use a lawn care service, contact the company to request that early spring nitrogen applications be limited.

Lawns can be fertilized in the spring. However, wait until the roots have stopped growing. In mid-May, apply 1 pound of actual nitrogen fertilizer per 1,000 square feet. Check the fertilizer package for application directions.

Then, apply plant food in November. This late-fall fertilizer application should provide enough fertilizer to stimulate the grass in the spring.

For more helpful lawn hints, pick up a copy of the Spring Lawn Care Guide at your local U of I Extension office. Or download a copy at http://web.extension.uiuc.edu/regions/sifamily -- it's the Tip of the Month in the Around the House section.

Source: David J. Robson, Extension Specialist, Pesticide Safety, drobson@illinois.edu

Pull date: March 23, 2007