The ideal time to prune most trees is during the dormant season. Advantages to dormant season pruning include:
- With deciduous trees, it’s easy to see the tree’s structure and the impact your pruning cuts will have on tree shape.
- Wounds close quickly during the period of rapid growth in spring.
- Sap flow from wounds isn’t excessive. This is key with trees that bleed sap, such as birches, elms and maples. Prune these trees in the heart of the dormant season – not close to spring – to limit bleeding.
- Disease transmission drops during the dormant season because disease organisms – and the insects that often transmit them – are also dormant. When some trees are cut, the wounds emit a chemical that attracts insects capable of spreading disease. For instance, oak wounds lure beetles that transmit oak wilt fungus. Wounds in elm trees attract bark beetles carrying the fungal spores of Dutch elm disease. With oaks and elms in particular, contact your local cooperative extension offices to determine proper pruning timing for your region.
- Insect attack decreases because insects are dormant. This is especially crucial when you’re pruning a tree frequently attacked by borers. If you prune when borers are actively mobile, tree wounds can attract the insects. Borers affect many types of trees, including oak, ash, birch and dogwood. Check with your local cooperative extension to determine which borers are most active in your area and when you should prune potentially affected trees.
Follow these guidelines to prune your trees at the ideal time of year.
Prune any time of year. Pruning during the dormant season minimizes sap flow. If you prune just before the flush of growth in early spring, new growth will quickly fill in and hide pruning cuts.
Hardwood Trees and Trees Without Showy Flowers
Prune during the dormant season. In areas where oak wilt is a problem, check with your local cooperative extension to discover the best time for pruning to avoid disease transmission. Typically, oak wilt transmission is most active from early spring through early summer.
Generally, prune during the dormant season. Exceptions include trees that flower in early spring, such as redbud or dogwood. Prune these immediately after they flower. With mature trees, dormant season pruning won’t diminish the spring flower show significantly, but with younger specimens, you may want to wait until after spring bloom.
Fire blight disease infects many flowering trees, including apple, crabapple, flowering quince, hawthorn, pear, mountain ash and pyracantha. This disease is spread by pruning. Avoid pruning from the time that spring blossoms appear until leaves fall in autumn. If you must cut these trees during this time, sanitize tools between cuts. For more on pruning tools, click here. Check with your local cooperative extension to confirm the best time for pruning to avoid disease transmission.
Exceptions to the Rule
The greatest exception to pruning rules relates to dead, diseased or damaged wood. You can safely remove these any time during the year without having a huge impact on tree growth and health. For more information on inspecting trees for these types of problems, click here.