Overwatering. If more than a few of the older leaves are yellowing, your gardenia may be dying from root rot due to overwatering or poor soil drainage.Gently tip it out of its pot, or if it's ...

Leaves on a young zucchini plant could be turning yellow because of under or overwatering.It could also be fertilizer burn, pests, diseases, transplant shock, low nutrition, or just a result of ...