Why do tomato plant leaves turn dark green and stems turn purple?
[1] As long as the leaves turn uniformly dark green and show no abnormal shaping, the tomato plant should be healthy. There’s always a chance that the leaves will have the lushest green because they’re where photosynthesis is being carried on. Proper amount of light plus proper chlorophyll show up as healthy green. The color also indicates that the plant’s getting proper nutrient amounts, especially nitrogen. But if fruit doesn’t develop, or if it develops too small, then the plant’s getting too much nitrogen. [2] Purple stems may or may not indicate stress. Sometimes it’s a sign of not enough phosphorus. Commercial fertilizers are ka NPK, for their emphasis on giving nitrogen, phosphorus, and potassium to the plant. Not enough phosphorus may mean exactly that. In that case, a fertilizer with a higher middle number [the P for phosphorus in NPK] or a superphosphate’s the answer. Or there’s enough of the nutrient. But the nutrient isn’t being made available in the proper amounts to the p
