Q.Hydrangeas With Brown Spots On Leaves
These are newly planted. Soil is red clay but I used topsoil mixed in with original potted material.
Certified GKH Gardening Expert
This usually happens when it is overwatered in attempted compensation for heat. These should be planted in a well shaded location, as full sun will bleach and kill them.
From here, you will have to use a fungicide, and correct watering habits which lead to bacterial spotting.
From experience, you can use fungicides on the plant itself, then use wettable sulfur and dolomitic lime in combination in the soil. This will condition the soil to prevent it from future infections.
Make sure that the soil dries, completely, down to about 3 or 4 inches between watering. These shrubs will tolerate some drying, and semi drought conditions.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm