Chlorosis comes following heavy rains for the following reason. Normally without a lot of rain, the pH of our alkaline soils will actually decrease right at the surface. When the pH falls, iron is released from being bound up by the calcium. When the iron is available for the grass, it becomes dark green. When the rain washes through, the pH returns to 8.0 and binds the iron. Greensand is an extraordinarily chemically complicated material and has a way to counteract the effect.
Brenda, when you have a question that is not identical to the topic you are reading, it is always best for you to post a new topic to get the best reader response. People are reading this topic about yellow St Augustine, not about invasive weeds. I will give you a hint as to the solution: proper watering and mowing height.
_________________ David Hall Moderator Dirt Doctor Lawns Forum
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