Q. There are 3 crepe myrtle in the back yard. One is very nicely shaped the other two were beside a patio overhang and side limbs were apparently removed to the height of the patio cover. So we have 2 very TALL 20 ft skinny trees with some green leaves at the top. I would love to prune the trees so they would grow out as opposed to up, thereby creating an umbrella shape to provide shade. Can I bend over the top branches and wire them to a more curved shape?
A. That is very unfortunate that these trees were pruned in this way. I can understand your disappointment. Once that these lower limbs were removed you are correct, the form was destroyed. I doubt very much that any new growth would occur in the lower canopy area from larger diameter limbs. So you are right, you would be able to pull some of these larger diameter limbs into position to form a more rounded canopy. Let’s talk a little bit about how to do this.
What you will try to do is to train the trees rather than prune them. Training is a different concept from pruning. Pruning is the physical removal of plant parts. What you want to accomplish here is encouraging the plant to grow into a different form by manipulation that does not involve pruning or removal of plant parts in the beginning. You will be bending the branches into a different position that is more eye-appealing. This involves pulling or pushing existing growth into areas where it does not want to grow. When you pull or push plant parts into different positions, this will cause the tree to respond to this change in its shape. After this response occurs over the next couple of years , you will then begin pruning to maintain and encourage this change in its form.
Timing when you pull these branches into place will be somewhat critical. You will pull them into place when they are supple and can bend easily without snapping the wood. You are lucky. Crape myrtle bends well. The wood is sometimes used for bow-making. Bending the branches is best when the sap is flowing in the spring. Your visual cue for this is when you begin to see new growth this spring beginning in February. Do not wait too long or you’ll miss this window. I would gauge this opportunity from early February to about mid-March.
The easiest would be to use non-abrasive cord, such as cotton clothesline, loop it around the branch you want to pull into place, pull it to the position you want and stake it to the ground. This position can be at any angle you want and in any direction you would prefer. Leave it tied in place for one growing season. That is enough.
Once the branches are pulled and tied in place you will see a change in how the plant grows. You will see more growth coming from the upper sides of the bent limbs. This is a response of growth to new sources of light. We call this type of growth phototropic. Roots grow away from light and called negatively phototropic. Less growth will occur from the bottom sides of the limbs because there is less light there than before.
As this new growth occurs from the upper sides of bent limbs is when you can begin pruning the tree --- if you want. The branches that grow will “fight it out” for light and grow accordingly. You can remove wood if it is objectionable to your sense of proportion and balance. In most cases your pruning cuts will be “thinning cuts” rather than “heading cuts”. Thinning cuts remove entire stems or branches back to a crotch and do not leave any stubs or partial stems or limbs. Leave the strongest and healthiest growth if it is in a place that you like.