Answer: Hydrangeas can be affected by a variety of foliage problems. Based on your descripition, I am not able to tell you if it is an infection or if it is related to transplant shock, or over or underwatering or possibly overfertilizing. In general though, good air circulation combined with good overall care can help prevent foliage problems. Keep the soil evenly moist like a wrung out sponge, not sopping wet and not dried out. Avoid wetting the leaves when you water. Use an organic mulch about three inches thick over the root area. Keep it away from the stems of the plant and spread it out in a flat layer. Plant the hydrangeas far enough apart without crowding so that they have good air circulating between them. These should be grown in morning only sun or in very bright dappled light all day. Afternoon only sun is intense and could cause heat stress. New plants would not need fertilizing, but next year you can topdress with compost and use a slow release or general purpose granular fertilizer such as 10-10-10 per the label directions.
If just a few leaves are affected, pick them off and dispose of them in the trash. If the discoloration seems to be spreading, I would suggest you consult with your local county extension or a professionally trained nurseyman to identify the problem more specifically. Based on knowing that, you can then decide how to treat them. In any case, this fall be sure to do a thorough clean up of all the fallen hydrangea leaves and put them in the trash to try to limit reinfection next year. Good luck with your hydrangeas!
Q&A Library Searching Tips