rhododendron issues: rolling, dried out leaves, yellowing of leaves

Asked August 8, 2019, 11:23 AM EDT

I have two rhododendrons that are being attacked by something. I can't see evidence of insects. The newest plant has its new growth rolling and drying out/dying off. The older plant is turning yellow for no apparent reason. Any ideas what is happening and how I can help them?

Howard County Maryland shrubs abiotic issues

5 Responses

Hi - I would like to have some more information in order to help us diagnose the problem. For the first plant with the curling leaves at the top, can you tell us:
- When was the plant installed? Was it newly planted this year?
- Have you used any herbicides near this plant?
- How much of the plant is affected?

The second plant with the older leaves yellowing appears to have different issues. To some extent, older leaf loss is normal in rhododendrons, but the yellowing may indicate problems with nutrition, soil pH, drought stress, or possibly a disease (or a combination of these). Are the symptoms throughout the whole plant or is it just one branch section that is affected? Have you tested your soil? (Rhododendrons like acidic soil and can't take up the nutrients they need if the pH is off.) Were there any changes to the planting area recently (tree or branches removed nearby to let more sun/heat on the plant)? Do you irrigate during dry spells?

If you could provide more information, that can help us hone in on what might be going on.

Christa

The rhododendron with the curling leaves was planted last year and hasn't had herbicides near it. It was hit by a falling pine tree branch during the early spring. When it was planted, I added better soil to the hole since the soil under the pine trees is predominantly clay. The curling is predominantly new growth at the top on about half of the plant.

The older plant is in a naturalized area under pine trees. The entire plant is affected and there are some branches that have totally died. I can't see any insects on or under the leaves or bark. The other rhododendrons and azaleas near it are thriving. I haven't checked the soil ph recently so don't know how acidic the soil is.

Your new rhododendron seems to be showing old insect damage. The stippling (tiny dots) are probably feeding. Those insects are gone now and no treatment should occur now. This is a cosmetic issue.

We would recommend watering both plants. Rhododendrons are shallow rooted. During dry spells (or droughts, which much of Maryland is going through now) they can always use a deep watering.

Rule of thumb: All new plants should be watered during dry periods for the first 2 years, from spring through fall. Be mindful that we often have highly-damaging fall droughts.

Your old rhododendron shows no obvious insect or disease. Water it deeply. It is competing with a huge pine tree, right? Same with your new one.

Ellen

Thank you so much for your expert advice. I really appreciate it.