Why are our oakleaf hydrangeas declining?
Our oakleaf hydrangeas are several years old and have been thriving. They were green and blossoming at the end of May. Three weeks later, the leaves are yellow and the plants are clearly dying. It was suggested that we water them well every few days and fertilize them, but we've had so much rain that that didn't seem to be the answer. Any suggestions as to what could cause this sudden demise?
We do not have enough information to diagnose the decline of the hydrangea.
Some possibilites include a root problem, vole damage, too much moisture, poor drainage, etc. It would be helpful to submit photos of the shrub - photo of the shrub and around the base of the shrub so we can see what you may be dealing with.
I hope these will help. Some seem to be coming back, or may not be dying as fast. I poked around the roots of some but didn't see anything that looked out of place--no growths or soft rot places. The plants are on the north side of the property against a fence, so west is on the left, east on the right. Drainage is toward the fence and down to the east. # 76 is the newest plant, put in last fall, and is the most western one. I have other shots that show more damage but they are too big to send.
Your shrubs are definitely under stress, but these are resilient plants and will recover. The reason for the browning, wilting, and dieback is obviously due to lack of water in the root zone, but the failure of the roots to take in and distribute the water may be due to poor planting technique. On the one hand, you could literally lift the plants out of the ground (carefully) and examine the root ball. If the plant was balled and burlapped it is essential that the burlap be totally removed allowing the roots to move laterally unimpeded. If the plants were container grown and the planting hole was dug in the shape of a bucket, the roots could also be seriously restricted. It would be helpful to loosen the soil in a rather wide radius around the root ball.
Alternatively, You can prune out all the dead wood, cut the plant back to a smaller size and encourage new growth.
Water thoroughly and frequently throughout the summer.