My shrubs need help

Asked October 27, 2020, 8:54 PM EDT

My hydrangeas developed a disease that made brown spots on the leaves and then many of the leaves turned completely brown and still hang from the branches, rather than falling off. This happened, this year only, to both my regular (came with the house) pink hydrangea (pic 1 below) and the 3 oak leaf hydrangeas I had put in about 10 years ago. The pink one only had 2 blossoms this year, but the oak leaf ones had more than that, but not as many blooms as usual. The pink one had problems first in April or May, then the others started looking brown around late July. It rained a lot this year, but I only watered the pink one once prior to late August, when its leaves were already brown. Also, the usually matching shrubs that line both sides of my driveway look very different from each other this year. On one side, they have their usual green leaves (pic 2) and on the other side the leaves are sparse and they look mostly like just branches (pic 3). This has been a gradual process. The 2 rows rows of these driveway shrubs were trimmed at different times in the spring, the side that is green was trimmed around April and the side that is sticks now was trimmed in May or June and seemed to be losing more leaves rather than growing them back through the summer. Is this a disease or did we trim it at the wrong time? You only allow 3 pics, but the leaves on the front side of a pair of another type of shrubs turned brown, while the rest of the leaves on both shrubs look fine. I could send pics later, but I understand "Ask the Expert" is closing down next week. Whom should I ask?

Wake County North Carolina

1 Response

Wow. So many issues. I'll answer the easiest first. Ask an Expert questions have been handled for many years by Extension Master Gardener volunteers. After Nov 1, the old program will transition to Ask Extension, but only a few counties will be supporting this, and Wake is one. You will need to go to our web site and submit your questions there. It may take a while to get the technology up and running.
As for hydrangeas, that first pic looks like a fungal leaf spot problem. Fungal problems typically don't affect flowering, which is controlled more by the temperatures of the previous fall or winter when the plant is setting buds. The unusually wet summer has also caused a lot of plants to develop root rot problems and it is difficult to diagnose which is causing your issues, just from photos. This could be the problem with your other shrubs. Your trimmed hedges problem does seem to be a matter of timing or amount of trimming. Most shrubs can't take more than 1/3 of their branches cut back at any one time, and the later in the year that they are pruned the harder it is to grow back. Heat stress can often add to the stress of being pruned. If those shrubs have not leafed out after 3 months, they may not. I would suggest giving them until next spring to see what happens. I also suggest raking up any leaves from under your hydrangeas after they drop to help prevent any fungal spores remaining near the shrubs.