Answer: Yellow leaves can be a sign of several things, including transplant shock for new plants; lack of nitrogen; or inability to absorb iron from the soil. If the new leaves are green, and the old leaves are yellow, it's probably a nitrogen deficiency. (Feed with a balanced fertilizer such as 10-10-10, or an organic fertilizer such as fish emulsion.) If new leaves are yellow, with veins showing green, the plant may be having difficulty absorbing iron from your alkaline soils. Apply a chelated iron source. Finally, gardenias do prefer a more acid soil, and as you probably know, our soils are in the 8 to 8.5 range. Even in improved beds, the soil tends to be alkaline. Add peat moss, pine needles (if you can find them), or gypsum to your soil to help reduce alkalinity. Once your plants regain their health, insects won't find them quite so attractive. Best wishes with your gardenias!
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