Careful, well-timed pruning leads to beautiful shrubs

Pruning is a science and an art. The science part is easy: simply take time to study it. The art comes with experimentation, observation and experience.

Some plants do great without much pruning while others need an occasional pruning, such as removing crossing branches and diseased wood. But make sure you use sharp pruning tools and study up beforehand to help ensure success.

Most pruning problems begin by planting a large plant in a small location. I often see photinias and Texas rangers planted in a spot the size of a shoebox. These plants grow fast and soon get out of hand. We try controlling their growth by constantly shearing them back to keep them small. Why not remove the shrub and plant something that grows slower or stays smaller?

Note what happens to shrubs when we are constantly shearing them. The first shearing causes excessive branching as lateral buds proliferate in response to the cut. The next shearing compounds the problem causing more lateral buds to break. Pretty soon, you have a bunch of little broom-shaped branch tips and unhealthy plants with bare patches in the canopy. And you the gardener end up with very few flowers. I see this all over town.

You can rejuvenate a sheared shrub but it takes time. Look inside the plant and remove the broom-shaped growth and dead branches. Follow the bad branch to where it attaches to a larger branch and remove it. Do this with hand pruners, but if you've sheared for a long time, you'll need loppers, or a saw.

Be careful not to flush cut where branches attach. Save the swollen area where it attaches to the main branch. It is within this collar, as experts call it, the activity that brings about quick healing of the wound.

To begin the reconstruction project, remove the old, weak stems. Continue until you've corrected the problem. Guard against removing more than a third of the live canopy during one season.

Here's another mistake gardeners often make: Pruning spring-blooming plants, such as pyracantha, in the winter. If you do this, you are removing the flower buds, and that results in no blooms that spring.

Prune summer-flowering shrubs, such as chaste tree, crepe myrtle and nandina, in the early spring before growth begins. If in doubt about when to prune any flowering plant, prune after flowering ceases. Like trees, never top shrubs; it weakens branches, causes lots of water sprouts and leaves behind dead stubs.

Now I am going to ask you to think backward when pruning older shrubs. Most gardeners remove the top growth and completely omit removing the older wood in shrubs. To do it right, remove the oldest wood at ground level, leaving the younger, healthier wood. This technique is especially well-suited for oleander, nandina and native shrubs. By removing the older wood, you'll experience blooms covering the plant rather than flowers sitting on exposed trunks. If you have a real old oleander, take away the wondering on what to prune and cut it completely back to the ground every five to seven years.

Here are some parting thoughts on pruning shrubs:

■ Pruning stimulates regrowth in proportion to pruning severity. Light annual pruning is better than periodic severe pruning.

■ The two basic types of pruning cuts are thinning and heading. Thinning is less invigorating, yet most effective for maintaining shrubs in their natural form. Heading promotes branching and increased growth.

■ Prune out horizontal branches and save those growing upward.

■ Plant characteristics such as flowering date or specific requirements dictate the time to prune.

■ Wounds heal fastest when you avoid disturbing the swollen area where stems attach to branch collars.

■ Wound dressing does not promote healing and can lead to disease troubles.

Linn Mills writes a garden column each Sunday. You can reach him at linn.mills@ springspreserve.org or call him at 822-7754.