Bypassing Plant Pathogens: Promoting Tree and Shrub Health Through Proper Pruning

Pruning in the winter can reduce the risk of disease-causing organisms infecting trees and shrubs through pruning cuts.

By Brian Hudelson, Plant Disease Diagnostic Clinic

Although it doesn’t seem like the optimal time to be gardening, February is actually a great time to be out pruning your trees and shrubs to make them more structurally sound and aesthetically pleasing.

Why prune now? Whenever you prune, you create wounds that potentially can serve as entry points for disease-causing fungi and bacteria. If you prune in the spring and summer (when it’s warmer and often wetter), these organisms are very active and more likely land on fresh pruning cuts and infect. When the weather is colder and drier (as it tends to be in February in Wisconsin), disease-causing organisms are much less active and the chances of them infecting though pruning cuts is much reduced.

How do I go about pruning? Check out University of Wisconsin Garden Facts XHT1013 (Pruning Evergreens), XHT1014 (Pruning Deciduous Trees) and XHT1015 (Pruning Deciduous Shrubs) for pointers on how to prune. Prune only when it’s dry, and decontaminate pruning tools between cuts (or at a minimum between each tree or shrub) by treating them with 70% alcohol (e.g., rubbing alcohol right out of the bottle, spray disinfectants containing ~70% alcohol) or (in a pinch) 10% bleach. Decontaminating tools kills off disease-causing organisms that you might pick up as you prune. Once done pruning, if you’ve used bleach, be sure to thoroughly rinse your tools, and oil them to prevent them from rusting.

By pruning regularly and taking a few simple precautions as you do, you will end up with trees that are beautiful, structurally sound and healthy.

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