Leaf Scorch

This is leaf scorch, not a disease or insect problem. The most common causes of leaf scorch include the following:
1. Plant getting hit with a household or garden product, liquid fertilizer, herbicide or hot water from a sun-heated hose. Although any of these can kill individual leaves, unless the entire plant is hit such damage seldom kills the entire plant.
2. Sunburn – this would normally happen if a plant is raised in a greenhouse or very shady spot and suddenly moved into strong sun. It might happen if a shading tree is suddenly moved. This doesn’t look like what has happened to your plant, but we list it to be complete.
3. Heat – exhaust from equipment working next to the plant etc.
4. Burn from being covered – if someone draped a tarp over the plant temporarily, for example, and that magnified the heat of the sun.
5. Salt spray. High wind off the ocean, salt water from other sources.
6. Drought combined with any of the conditions above.

Sometimes we don’t ever figure out what damaged a plant, or it might suddenly occur to us after time goes by. In any case, since it’s the end of the season and these plants will soon lose their leaves it’s unlikely that your shrub will be permanently damaged. Water the ground all around this hydrangea very well to wash anything out of the soil that might have been applied to the ground as well as the plant. If you want to be really nice to this shrub, apply a layer of composted manure all around the plant on the surface of the soil.