How To Care For Sick Hydrangea. Its best to start with a low dose of fertilizer. Shake them off cut the bottom of the stem and place them in water with flower food.
When you wash the next day simply rinse the hydrangeas under a running faucet. Fertilizing once or twice a year is likely enough for you to care for your Hydrangea. You can use an organic fertilizer such as compost or a special hydrangea fertilizer from your favorite garden store.
If summer rains make the problem worse try a fungicide such as Immunox always follow label directions.
Another option is to use neem. Hydrangeas can also be transplanted easily but this should only be done during dormancy in fall or winter. Give the hydrangea a thorough soaking at the base daily for the first week while the plant gets established. Make sure to keep your arrangement out of direct sunlight.