Pruning Trees and Shrubs – When and How

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It’s a necessary thing – to prune.  Prunes can be important for human health too, but that’s for another blog.  Removing unwanted or broken/diseased stems is important for the health of the woody plant, but perhaps even more important is the timing of the action.  Some pertinent specifics follow:

 

Shade trees:  the best time for pruning is in the April to June timeframe.  Recent research indicates that trees close pruning wounds and recover from the loss of the photosynthetic surface best in spring when surrounding tissues can grow more quickly.  Fall pruning usually leaves the cut surface open to the elements for a longer time, which leads to desiccation and slow recovery.  Two species which are the exception to the rule are elm and oak, which should be pruned in late winter due to the potential for disease infestation from insects that transfer the inoculum.

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Evergreen Trees:  Evergreens produce new growth only from the terminal ends of the branches; as such, recovery from removal of limbs tends to be slow, leaving open areas of the tree.  Yet, if a branch is broken or diseased, removal may be necessary to retain a healthy specimen.  Generally, entire limbs should be removed, rather than cutting off a limb at a middle point of the length of a branch.  For both shade and evergreen trees, it’s best to contact an NAA or ISA Certified Arborist for a consultation and the pruning itself.

 

Flowering Shrubs:  A “recipe” of sorts is appropriate for flowering shrubs.  If the specimen blooms in spring, it’s blooming on wood that was produced the year before, so it’s usually wise to wait until after flowering to enjoy the floral display and to avoid damage to tender stems.  If the shrub blooms in summer, it’s blooming on current season growth, so early spring pruning is best.  For both species, thinning is the style of pruning that is most healthy, rather than a simple shearing off of the growth, which is common for yews, coralberry, honeysuckle and boxwood.  If you want to prune to produce an unhealthy shrub, go ahead and shear it.  Instead, remove about a third of the stems at the ground level each year…don’t leave a foot of growth or even a couple of inches…remove the entire stem.

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Non-flowering Shrubs:  Non-flowering shrubs such as privet and burning bush should be treated in the same manner as for summer blooming shrubs, with a stem removal in May.  Focus on the older, thicker stems.  If the plant has gotten overgrown over the years, a rejuvenation is in order, where all the stems are removed at ground level, allowing the regrowth to become the new structure of the shrub.

John Fech
Horticulture Extension Educator at Nebraska Extension
John Fech is a horticulturist with the University of Nebraska-Lincoln and certified arborist with the International Society of Arboriculture. The author of 2 books and over 200 popular and trade journal articles, he focuses his time on teaching effective landscape maintenance techniques, water conservation, diagnosing turf and ornamental problems and encouraging effective bilingual communication in the green industry. He works extensively with the media to extend the message of landscape sustainability, making over 100 television and radio appearances each year.
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