We have gotten several questions about rhododendrons that have droopy leaves. Generally, when you see a plant with leaves flagging or hanging droopy you know that the plant is not getting water for some reason. There are several reasons why a plant is unable to uptake water.
Why Droopy Leaves - A plant can have droopy leaves due to simple drought. We had warm dry days last week and very little rain. Perhaps plants just did not get enough water. In the spring, plants will try growing rapidly during warm weather and therefore will need water. If there has been little rain a plant can get drought stressed.
Droopy leaves can be caused by the water not getting up the stem for some other health related issue reason. If drought is eliminated as a cause of the flagging then we might suspect some lower stem, root or environmental problem. Anything that inhibits water flow up from the roots can cause drought-like droopy leaves.
Voles - The first thing to do is to pull back the mulch under the shrubs and look for 1/2 holes/tunnels in the ground. If you see this you have voles. Voles nibble roots on shrubs and trees.
Rhododendron Borer -If you find any sawdust coming from the base of the plant you need to treat the plant for rhododendron borer with an insecticide .
Root Rot - A root disease will kill the tissue just under the bark. Skinning back a little bark on the lower stem should reveal green tissue if it is healthy or brown dead tissue if there is a disease.
Spring Evergreen Leaf Drop - In an evergreen plant, yellow older leaves are caused by a lack of nutrients, specifically nitrogen. In the spring, if the plant does not have enough nutrients when the spring growth begins, then the plant will rob the older leaves of nitrogen and move it to the new buds. In this case, some water soluble fertilizer such as Miracle Gro would be useful (follow labelled directions).
