Many Rhododendrons in the landscape look like this at this time of year in the Northeast. It is a sign of stress, and could be root rot, other root or stem damage from the winter, a combination of sunburn and wind burn, or a combo of all of these. With plants sometimes what we see isn’t the result of just one thing but several combined.
1. Without culturing in a lab we can’t know if it’s phytophthora or not. That will be a time-will-tell kind of thing.
2. Look at the bottom of the plant – examine the stems carefully, especially from ground level to about 8″ up. Plants that have been in snow are sometimes girdled by mice or voles eating the bark all the way around the plant. Once the bark is eaten, water is no longer carried up the stems to reach the leaves, so they curl.
3. Are these plants on a sunnier or windier side of the house? If so, this cold be sun or wind burn. Sunburn is especially hard on Rhodys when there has been a snow cover, since the sun reflects off of the snow and draws moisture out of the leaves. In such situations when the ground is frozen the plant can’t replace the moisture that the sun/wind has drawn out and the leaves curl.
4. Are these a different variety of Rhododendron from your others. Different hybrids/species/cultivars are more or less sensitive to winter burns and stresses. In many landscapes you can see plants right next to each other and one variety is yellow and curled while another is healthy looking and green. The interesting thing is that in two months both plants look fine – the “damage” done to the curled one goes away as the temperatures warm.
At this point, other than considering the above, you should wait and see if these plants do indeed recover later in May. Provided that they don’t have girdled stems (no recovery from that) you could apply a light application of an organic fertilizer and an inch of compost or composted manure all around the plant under the dripline and then wait to see if there is recovery. If they still look bad in mid-to-late-May you’ll know they are gone. If water/drainage is an issue there don’t plant Rhododendrons again – consider Winterberry Holly, red-twig dogwood or other moisture-tolerant plants.
Leave A Comment