Late 90's drought combined with this winter's weather slams rhododendrons

Don't panic over or give up on those shriveled rhododendrons—at least not yet.

That's the message from Extension Educators of UMass Extension's Landscape, Nursery and Urban Forestry program, who have been fielding a barrage of phone calls statewide regarding apparently devastated rhododendrons-especially larger, older plants in established landscapes. Callers are reporting tightly curled, limp, off-color leaves on many plants.

The good news, according to Extension Educators, is that the affected plants are, for the most part, not infested with insects such as black vine weevil or rhododendron borer,  or infected with diseases such as Botryosphaeria cankers, and that at least part of the plant may recover.

The bad news is that the worst looking parts of the plant may simply have died from lack of moisture.  One of the reasons for this was a dry period last fall, when rainfall was 3-4 inches below normal.  Other conditions that may have contributed to this problem include sudden temperature changes, a prolonged cold winter, and a lack of a January thaw.  Educators also suspect that the persistent snow cover that increased the reflection of light and caused leaves to evaporate more moisture than normal, and therefore adding extra stress to those plants.

Whether the plant will fully recover is anybody's guess.  UMass Extension educators recommend the following: Do not spray with pesticides or fertilize the plants now.   Water the rhododendrons once a week during hot and/or dry periods.  Apply a soaking type of irrigation that wets soil to a depth of 12-18 inches.  Long-term rhododendron health requires maintaining 2- 3 inches of mulch over as much of the root zone as possible. Once it is certain that a part of the plant is beyond recovery, prune and dispose of dead twigs or branches, which can be potentially invaded by opportunistic pathogens and insects. 

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