Dahlia leaves turning yellow

Asked August 21, 2018, 9:52 AM EDT

I planted some dinner plate dahlia tubers in May. Within the past month, the leaves on the bottom of the dahlias have been turning yellow, wilting and falling off. Some of the leaves have a white film on them as well however, the top leaves and flowers look completely healthy. The leaves are becoming more and more sparse towards the bottom. Any idea what could be causing this?

New Castle County Delaware

1 Response


It has been an unusually wet summer, so I suspect that the roots of the dahlia have not gotten well established. Do not add fertilizer until roots have developed a bit. There does look to be some fungal growth we call powdery mildew on the upper surface of those leaves, it is also favored by high humidity. Try to avoid water on the leaves. Water the base of the plants deeply once a week if there is no rain. You may also want to have a soil test done to make sure the nutrient levels and pH are correct. Here is the soil testing lab info: http://extension.udel.edu/dstp/
Pick off leaves that are affected and discard. Hopefully your dahlia will coe back more full next season.

Thank you for contacting Cooperative Extension,