Answer: Iron chlorosis is sometimes an issue in the West because of alkaline soils. Chlorosis is recognized by new leaves that are yellow, while the veins remain green. If the condition is severe, the entire leaf may be yellow. Although iron may be present in the soil, it is not always in a form that plants can use. Overly wet soils are depleted of oxygen. (As water fills in the minute spaces between soil particles, air moves out.) Plant roots need oxygen to absorb iron in the soil. To help prevent chlorosis, always water slowly, deeply and infrequently. Soil with a high pH (alkalinity) also inhibits iron absorption. If you are using correct irrigation methods and symptoms are still present, apply iron chelates or ferrous sulphate to the soil. Both are readily absorbed by a plant?s roots. However, if older leaves are yellow while new leaves are green, it may be a nitrogen deficiency. You might want to take samples of the leaves to a full-service nursery or your County Cooperative Extension office for a complete diagnosis. Denver County Cooperative Extension, 110 16th St., Ste. 300 Denver, 80202, 640-5270. Good luck!
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