How to fix these rhododendron (or azalea?) bushes
I am unsure of the condition of these bushes before I moved here, but I first noticed problems last summer during periods of high temperature in the summer, and low rainfall. After leaves curled and several branches died, I started watering when it wasn't raining in the summer, but the plants were definitely stressed. They are on an eastern exposure and get a lot of sun. The watering doesn’t seem to have helped the health of the leaves, as they are still bronzed and somewhat sparse. I wondered if it might be the soil pH, or lacewing bugs, so I tried an insectidal soap to adress that, and I doused the bushes with water mixed with fully chelated iron, but I feel like I’m really guessing, and perhaps wrongly. The underside of a new leaf from a sucker doesn't appear to me to show signs of lacewing bugs. Would it at this time of year, or is it too early for them? I tested my soil with a home tester, but am also unsure of its accuracy. What do you think I should do? Thanks so much!
Ingham County Michigan
From the pictures, I would surmise that these are rhododendrons that are water stressed especially since they look like they are in full sun (and prefer part shade).
First I would suggest you begin with testing the soil to determine if there is something you need to do to improve the soil health. Below is the MSU web site where you can learn more about the soil test process and also purchase the $25 kit. It takes about two weeks for the test results to be completed and emailed to you. Once you receive them, feel free to contact the toll free Lawn and Garden Hotline at 888-678-3464 and an Ext. Master Gardener can review them with you as needed.
As for the shrubs, scrape your fingernail across the bark to see if there is any green underneath. If not, the limb can be considered dead and can be pruned back to live tissue. We would usually recommend pruning rhodos after they bloom but if there is a good deal of dead wood on the shrub, pruning before bloom won't hurt the plant. Water during dry periods and apply rhodo fertilizer before and during the bloom season (following application rates/times on the label). You should know by the end of summer if they have recovered back to a state of good health and growth. If not, then I would suggest moving them to a shadier, more protected site.
Hope that helps and good luck!