When to Trim Evergreen Bushes

Light trims are safe for evergreens at any time of year.

Trimming evergreen shrubs can shape them, shorten them and shed dead branches -- but the wrong timing can be fatal. While a poorly timed prune won't kill evergreens, it can weaken their health and make the next trim more dangerous. On the other hand, careful timing ensures that evergreens retain their strength and robust look.

Seasonal Timing

The safest time to prune most evergreen bushes is in late winter, near the end of the dormant period. This spares shrubs from the stress of winter weather. Because pruning encourages new growths, it also produces thick foliage just in time for spring. Bushes that flower in spring as opposed to summer, however, may prefer mid-summer pruning, as this reduces the risk of gardeners snipping off young buds and reducing flowering.

Warning

Pruning in spring and autumn are the most dangerous times for evergreen health. New foliage in the spring produces food -- which means cutting it off in spring may limit an evergreen's food supply and cause dwarfing. Meanwhile, pruning in autumn inspires new growths that may not harden off before winter hits. Freezing temperatures, frost and ice may damage the new growths and leave a bush weak and thin.

Problem Branches

If any part of an evergreen bush experiences problems -- such as broken branches, disease or insect infestations -- immediate pruning can save the rest of the plant. Seasonal timing is less important for these trims, as gardeners must act fast to prevent the problems from spreading.

Considerations

Though seasonal timing is critical for extensive pruning jobs, light trims rarely harm plants. This is especially true for evergreens, as they cycle out their foliage year-round and maintain a bushy appearance even in winter. Horticulturalists characterize a light trim as pruning away no more than 10 percent of foliage.

References

• AgriLife Extension: Follow Proper Pruning Techniques; Douglas F. Welsh, Everett Janne; November 2008
• Iowa State University Extension: The Proper Time to Prune; Richard Jauron; Feb. 11, 2000
• Washington State University: Spokane County Extension: Pruning Evergreens; Tim Kohlhauff; January 2005
• Colorado State University Extension: Pruning Cuts; David Whiting, Robert Cox, Carol O'Meara; July 2009

Resources

• Virginia Cooperative Extension: A Guide to Successful Pruning, Shrub Pruning Calendar