Gardening With Allen: Restore shrubs’ shape by pruning

My shrubs have been sheared so they are thick and unnatural. Can I do some pruning that will bring them back to their natural shape and thickness? Is now a good time to prune?

Yes, shrubs that have been sheared so they have lost their natural shape and thickness can be recovered. Now is a good time to prune most shrubs. It is important to prune spring flowering shrubs right away. They begin forming new flower buds for next year in August and September.

Shrubs that have been sheared can be pruned to restore a more natural shape and thickness. However, it may take more than one pruning to recover. When shrubs are sheared, the tips of all the branches are pruned. This causes them to produce multiple side branches. The first shearing causes about three branches to develop where there was one before. The second shearing produces about nine branches to develop. After the third shearing there are 20 or more branches.

Start by following a branch down inside the shrub one or two layers below the outer branches. A single cut deep inside will remove multiple branches outside. By removing about a third of the branches this way, the shrub is opened up and no longer looks so crowded. The adjoining side branches will fill in where a major branch has been removed.

If the shrub has been pruned into an artificial square shape, the branches on the corners are shortened more to give them a round shape. Don’t prune so severely that all the leaves are removed on the corners. It may take several prunings with a year’s growth between them to completely recover.

Don’t prune all branches to the same length. The variety of lengths will give the shrub a more natural appearance. I like to start at the bottom of the shrub and gradually prune branches shorter as I move up. This gives a rounded or curved natural shape. Prune so that upper branches are shorter than lower ones. If lower branches are pruned too short, they become shaded by the upper ones and start to lose their leaves.

Some deciduous flowering shrubs that have become overgrown can be drastically pruned back to within a few inches of the ground. They will quickly grow new branches that can be pruned to retain a natural shape. Nandina, rhododendron, red twig dogwood, barberry, potentilla, spiraea and lilac will all respond to this type of pruning. Remember, however, that you are sacrificing at least one year’s flowering when you do this. Potentilla will bloom the next summer after being cut back in the summer.

Where branches are growing out over the lawn, consider widening the bed so you have more room for the shrubs. Where shrubs are growing over a walkway or blocking windows, your best choice may be to remove them and plant shrubs that grow smaller.

If you would like a copy of my more detailed leaflet on natural shrub pruning, send me your email address.

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