A while back I used the term “follow the flower” regarding the correct time to prune spring flowering trees and shrubs. The same principle applies to late spring and early summer bloomers as well. I spent the last couple of days in my garden pruning my large leaf rhododendron– pruning stem by stem to maintain their natural appearance, as opposed to sheering them into geometric shapes.
Large leaf rhododendrons tend to grow a bit erratically, with many stems growing at a uniform rate while others can add on two to three feet of growth during the same time. This long erratic growth is what I remove, and I do a bit of height control pruning as well.
Often you will see large leaf rhododendron that have grown too large for the space they are in. One solution to this problem is to limb them up. Remove all the bottom branches to three to six feet above the ground. This removes the widest part of the shrub and exposes the beautiful understory branching below. These tree form rhododendrons add interest to the landscape and open up new planting areas in the garden below.