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Fertilizer: Fact of Plant Life or Fiction?

Soon the advertisements will be in every form of media – newspaper, TV and radio. All will tout the same message. “Purchase fertilizer now!” But does the marketing accurately express the need?

Research demonstrates that all plants including grass, shrubs and trees, use nutrients applied in the fall more efficiently and to greater effect than those applied in spring and summer. This is especially relevant to nitrogen, the nutrient most critical to plant growth. So, our landscape plants need nitrogen, right?

Yes, but very little as long as you practice proper gardening techniques:

  • Warm season grasses require 2 pounds of nitrogen per 1,000 square feet annually; clippings from properly cut grass produce about that much.
  • Woody plants require about the same amount of nitrogen, but their larger root systems provide more opportunities to extract it from the soil. Leaves mulched and left on the ground provide about the same amount of nitrogen annually.
  • Carbon is necessary for microbial energy. So add compost to the lawn once a year and mulch to beds in May and September.

Vegetables are another story and best left for a future article. If your life is now bland and gray because you’ve discovered fertilizers could be unnecessary, then use organic products with less than 8 percent nitrogen and enjoy life again.

Mark Peterson
Mark Peterson
Mark A. Peterson is a conservation project coordinator for San Antonio Water System. 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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