Rhododendrons: newly planted rhodo suffering

The following was received via email:

Hi, I had purchase a Henry's Red Rhodo and planted on a good spot need my other rhodo alread well establish, the bloom was wonderful, and now for about 3 weeks now, out of the sudden, all the leafs of my shrub, all went down, like it was winter and all curl up...I don't see any mildew on it, and I don't believe it was too much or not enough water...so I don't know what is happening with it.....I repoted my shrub back in the original back I purchase it, and hope maybe to save it that way....Do you have any miracle solution and any suggestion for me to try to same my wonderful shrub..

Thank you for your cooperation.

 

If your rhododendron is suffering in the way you describe (drooping, curled leaves), there are several possible causes, but they all stem from the same general condition; i.e., insufficient moisture getting to the leaves.

Too much water (even in the middle of summer) can be a problem if roots are submerged for extended periods. Similarly, if roots are kept dry they won't last long. In both cases, root tips die and the roots are unable to transport water effectively. Waterlogging is seldom a problem at this time of year, except where the soil is heavy (fine-textured). The most common problem in summer is drought at depth. This is particularly common with newly planted shrubs. For example, with a plant originating in a two gallon (#2) container, the bulk of living roots may be at a depth greater than 20cm (8") below the soil surface once planted. Water applied at the surface may not reach these depths for a considerable time, and many new gardeners often under-estimate the amount of water necessary to reach this depth. Another problem with newly planted material concerns air pockets. In the planting hole, if the soil doesn't make intimate contact with the root ball of the plant, any roots exposed to the air pocket will die.

Finally, there are a number of insect pests that can cause this kind of damage if they have consumed root tips or girdled the stem of the plant. The most common rhododendron pest is the black vine weevil, the larvae of which can chew through the bark of a small rhododendron completely undetected, because they feed immediately below soil level. Unfortunately, many nurseries continue to sell rhododendrons and other plants with weevils infesting the soil. The best way to check for their presence is to knock the plant out of the pot (at the nursery) and check for feeding damage around the stem. Adult weevils feed on leaves and cause a characteristic notching along the edges.