Question: I purchased a potted kumquat last spring, and during the fall and winter it developed yellow blotches on its leaves. Now it is February and there is a lot of new growth on the branches. The new growth hasn't developed the yellow blotches. Any idea what is causing this yellowing, and should I be doing something about it?
Yellow leaves can be caused by many things including lack of nitrogen, insufficient light, water-logged soil (plant roots need oxygen to thrive), dry soil, or iron deficiency. If the older bottom leaves are yellow, but new growth is green, the plant may be suffering from a lack of nitrogen, or may have dried out at some point. If new leaves are yellow with green veins, the problem may be a lack of iron. (Lack of nitrogen is a more common problem than lack of iron.) Soil should be kept moderately moist (but not wet). The yellowing could also be the result of transplant shock or being moved from an ideal greenhouse or nursery environment into your home. Since the new growth is healthy and green, the latter is the likely explanation. Just keep up a regimen of good cultural practices (appropriate water, sunlight, fertilizer) and your kumquat should be fine.
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