Hydrangeas sometimes get a burn on the leaves in the summer. This is called 'hydrangea leaf scorch'. This is a physiological problem not pathological (disease related). When temperatures climb relatively quickly, hydrangea leaves can scorch when water can't get to the leaf from the roots quickly enough. Hydrangea leaves can also scorch when the soil gets dry or if the leaves get too much sun. Luckily, this is not a disease and it will not kill the plant. Irrigating plants during hot weather can help alleviate hydrangea leaf scorching.