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Chlorosis Diagnosis? Follow the Geekster’s Orders!

Are yellow leaves making you blue? Leaf chlorosis or yellowing of leaves is a common problem for plants in alkaline soils – the very soils found in San Antonio. Alkalinity binds iron to the soil, preventing plants from absorbing it. The result: yellow leaves.

But chlorosis happens for other reasons, too. You just need to be a bit of a gardening sleuth to determine the cause.

  • Watering with reckless abandon? Too much water keeps roots from functioning properly and prevents nutrients from reaching leaves.
  • Frequently fertilizing? Excessive applications of phosphorus also binds iron to the soil.
  • Killing weeds? Many herbicides turn the leaves of unintended target plants yellow.
  • Root-bound plants? Plants with damaged roots or that have been kept in a pot too long display yellow leaves.
  • Pesky issues? Insects such as chinch bugs or viral diseases like as St. Augustine Decline turn leaf blades yellow or striped.

Once you determine the cause, making things green up again is simply a matter of applying the right treatment. This might be turning off the spigot or ceasing fertilizer application. Pest problems may require direct action with chemical or predator products. For simple alkaline-induced chlorosis, try an iron supplement that actually works on soil. (I recommend Iron Plus or greensand.)

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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