Hydrangea burn or disease

Asked August 3, 2019, 8:18 AM EDT


I planted several hydrangeas this year and ran into a problem during the heat wave we had a few weeks back. I was out of town so they did not get additional watering, and i'm trying to determine if the attached issue is just burnt leaves or a larger problem. About two weeks ago there was little to no green left on the plant. I've installed a drip line that has helped bring them back with some new growth, but if the black/spots on the leaves are a disease i believe i need to do something else.

Any advice on if this is just burnt leaves (to the extreme) or a larger leaf spot problem would be very helpful. Thanks for any help you could provide.

Montgomery County Maryland disease issues shrubs hydrangea plant care abiotic issues hydrangea leaf spots and dieback

1 Response

You're seeing both leaf dieback (often from the leaf tips) as a result of dry roots, and also a fungal leaf spot.

When plants get too dry (and hydrangeas hate dry soil), some roots dry up and die. This means even when water levels improve, there are fewer roots to supply moisture to the plant. Roots will regrow, but meanwhile some leaves will be damaged when they get too dry.

The fungal leaf spot disease (small spots) on some of the leaves is very common on hydrangeas, but doesn't appear every year usually. It is a fungal disease that rarely does much damage to the plant, but can be unsightly. It occurs when there is lots of rain or it is very humid. It can be treated with a copper based fungicide if you feel that you really need to treat it. Don't spray when it's too hot--it can burn the leaves. Read the label very carefully. Fungicides are preventatives, not curatives, and since it is so late in the season the spotting damage is mostly done. There isn't much point in spraying now.