Why are the new leaves on my bigleaf hydrangea yellow?
Bigleaf hydrangea is susceptible to iron chlorosis. Because, iron becomes less available as pH increases, iron chlorosis is most likely to be found on plants growing on high pH soil. In contrast to nitrogen deficiency, which is expressed as yellowing of old leaves, iron chlorosis is found on new leaves (see image at right). Iron chlorosis can be corrected by the addition to iron to the soil. The best way to do this is to use a chelated iron product. You should be able to find one of these products at a garden center or the garden section of a hardware store or mass merchandiser. Follow package directions carefully. You should begin seeing results in a couple of weeks. As long as the soil pH remains high, you will probably need to re-apply the chelated iron product yearly or whenever symptoms reappear. Lowering soil pH through application of aluminum sulfate or mulching with acid organic materials like pine bark is a long-term solution for iron chlorosis.
