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Fertilizer: Plant Life Fact or Fiction

Our landscape plants need nitrogen, but they don’t need as much as you think, especially if you practice proper gardening techniques.

Soon advertisements will be in every form of media. All will tout the same message: to purchase fertilizer now. But does the marketing accurately express the need?

Research establishes 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 true regarding nitrogen, the nutrient most critical to plant growth. While our landscape plants need nitrogen, they don’t need as much as you think, especially if you practice proper gardening techniques.

  • Warm season grasses require 2-5 pounds of nitrogen per 1,000 square feet annually; mulched clippings from properly cut grass and compost supply about that much.
  • Woody plants require about the same amount of nitrogen, but their larger root systems are better able to extract the necessary amount from the soil. Leaves and grass clippings that are mulched and left on the ground provide approximately the required amount of nitrogen annually.
  • Carbon is necessary for microbial energy. So add compost to lawn and beds once a year in early spring or late fall and mulch to beds in May and September.

If you’re still feeling the urge to fertilize, instead use organic products with less than 8 percent nitrogen in early May and October 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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