Fertilizer is Rarely Necessary

Although I love the color green — green leaves, green T-shirts, green tea — I don’t particularly care for rivers, lakes, aquifers and a Gulf of Mexico made green by excess fertilizer.

Often thought of as just St. Patrick’s Day phenomenon, rivers occur when homeowners and property managers think March is the time to fertilize the lawn. You see, fertilizer encourages algae and duckweed, which turn bodies of water a murky green hue, particularly when fertilizer is applied before a plant’s roots are active — usually the third week of April.

Warm season turf grasses like Bermuda, zoysia or St. Augustine don’t become active until about the first week of April. And, our usual recommendation is to cut the lawn twice before even applying fertilizer.

Woody perennial roots such as on flowering shrubs and trees become active earlier, usually the first or second week of March. Still, fertilization should be done only when leaves are fully developed, typically in late April or early May.

But let’s step back for a moment. Do we really even need to fertilize? According to research studies, Bermuda grass needs about 2 to 3 pounds of nitrogen per 1000 square feet, per year, to stay green and actively growing. Mowing often and leaving the clippings on the lawn provides about 1 ½ to 1 ¾ pounds of nitrogen to your lawn. Compost can fill in the shortage if necessary. No fertilizer required.

And for woody plants, compost and shredded leaves are more than adequate nutrients. Now, if your plants appear thin and yellow, a wee amount of fertilizer can help give them a boost. But overall, fertilizer is not always a necessity.

We can limit the amount of nitrogen and phosphorus entering our rivers and aquifers by only using fertilizer at the right time and in the right quantity.

Picture of Mark Peterson
Mark Peterson
Mark A. Peterson was a conservation project coordinator for San Antonio Water System before retiring. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you're likely to find him hiking San Antonio's wilderness parks or expounding on the virtues of geography and history to his friends.
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