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From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Chlorotic leaves on yaupon in Austin
Answered by: Barbara Medford
We looked up "chlorosis" in Botany for Gardeners by Brian Capon (see Bibliography below) and learned that "the characteristic deficiency sympton of magnesium and iron is chlorosis (yellowing of the leaves) due to the curtailment of chlorophyll synthesis. Magnesium is an integral element in chlorophyll molecules; iron must be present during production of the pigment."
From the University of Illinois Extension, this article Focus on Plant Problems has very good information on the reasons for cholorosis. You need to read the whole article, as it has suggestions for treatment, but we felt the first paragraph probably summarized what you need to be looking for:
"Chlorosis is a yellowing of leaf tissue due to a lack of chlorophyll. Possible causes of chlorosis include poor drainage, damaged roots, compacted roots, high alkalinity, and nutrient deficiencies in the plant. Nutrient deficiencies may occur because there is an insufficient amount in the soil or because the nutrients are unavailable due to a high pH (alkaline soil). Or the nutrients may not be absorbed due to injured roots or poor root growth."
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