Pruning tips for trees, shrubs and espaliers

Pruning is at the top of the to-do list in your July garden. Prune out water sprouts — vigorous shoots on the inside of a tree and on the trunk — and suckers, vigorous shoots growing from the base of the tree. Crabapples and hawthorns tend to send out lots of water sprouts, so they can benefit from this kind of pruning.

You’ll also want to prune shrubs that put on a lot of growth this year; prune as needed to keep them at the right scale for your garden. Growth will be mostly hardened off by now, so there should be minimal new growth if you prune at this point in the season. Try using a pair of hand pruners instead of an electric hedge clipper to create a more natural look by making individual pruning cuts at different heights throughout the shrub. For a more formal look, make cuts at the same height. Prune right above the leaves to help hide the cuts. Careful pruning leaves the plants smaller but not looking “sheared.” Remove dead wood as necessary, too. Spring flowering shrubs like lilacs and viburnums are setting flower buds around now, so take that into consideration when you’re pruning so you can minimize flower loss for next year.

For espaliered plants, keep pruning as they send out new growth to keep them looking crisp. Usually this means trimming them several times over the course of the summer to maintain the best appearance.

If you have a pine with new growth at the tips of its branches that has turned brown, a disease called Diplodia tip blight could be the problem. The disease is more common on trees that are under environmental stress, and trees older than 15 years. It’s too late to spray fungicides now since infection occurs in the spring, but prune out dead tips in dry weather to reduce the spread of infection. Be sure you disinfect pruners in between plants when pruning out diseased branches; I use Lysol disinfectant to sanitize my pruning tools as I go.

Correction on grubs

Please note: a previous column mentioned using a fungicide to treat a grub infestation when it should have said insecticide.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.