Why Are My Rhododendron Leaves Curling and Wilting?

Rhododendrons are sturdy, generally trouble-free evergreen shrubs beloved for their beautiful spring blooms, so it can be startling when you notice that a usually healthy plant's leaves are curling inward. Depending on the season, there are actually several reasons these shrubs might start looking unhappy. Use this simple checklist to find out what’s wrong, and learn how to fix the problem—then you can go back to admiring the year-round beauty of your rhododendron. And here's a pro tip: After the blooms fade, remember to deadhead (pinch off) each cluster of flowers, called a truss, at its base. If you do that each year, you’ll be rewarded with lots of flowers the next spring.

Rhododendrons Curl Their Leaves Against Winter Wind

If your rhododendron shrub is exposed to too much cold winter wind, it will curl its leaves inward, trying to keep less leaf surface exposed. The shrub is trying to keep water from evaporating from its leaves. Here’s how to help: Whenever the temperature gets above freezing, give your rhododendron a slow and steady trickle of water until the soil feels damp 8-10 inches down.

Keep that needed moisture in the ground by adding two inches of mulch. The mulch layer should cover an area starting two inches away from the trunk and going out beyond the ends of the branches. Next fall, get your rhododendron ready for winter by giving it at least an inch of water (from you or from rain) each week. You can also move your rhododendron to a place with protection from winter wind to alleviate this problem.

Rolled-Up Leaves in Summer Could Be a Sign of Dry Soil

Like any other plant, when a rhododendron doesn't get enough water, it will wilt. The shrubs have fairly shallow root systems, so they need a regular supply of water. If rain isn’t falling, you have to turn on the sprinklers or get busy with a hose. And check that you have at least two inches of mulch around your plant to keep water in the soil from evaporating. If you can, use pine bark mulch, as it creates the acidic soil rhododendrons prefer.

Too Much Water Can Cause Curled Rhododendron Leaves

Rhododendrons can suffer from root rot if they're not in well-drained soil. Putting one of these shrubs in a wet spot in the garden is always a mistake. A pathogen called phytophthera takes hold in overly damp conditions. To see if this disease is the problem, you'll need to do a little digging. Because these shrubs have shallow roots, you won’t have to dig too far to get a look at them. If the roots are mushy and black instead of firm and tan-colored, root rot has set in.

Treating with a fungicide won't help, but to see if your shrub can recover, you could try moving it to higher, better-drained ground, or into a raised bed. Clay soil holds onto water, so if that’s what you have in your garden, be sure to add plenty of compost or pine bark to the new planting area. Don't plant another rhododendron or azalea (they're close relatives) in the old location, as the pathogen will attack the new plant, even one specially bred to be disease-resistant.