Pruning Guidelines

Every summer I receive calls asking, “Can I prune trees now or when is a good time to prune?” Unfortunately summer is not the most ideal time. The preferred time is late winter or early spring while the trees are still dormant. This is true for deciduous and coniferous woody plants. In North Dakota, March is generally the best time to undertake this work to minimize excessive sap flow. Exceptions to this would be trees noted for heavy sap flow such as maples and birches. Pruning of these species can be done after full leafing out is complete.

Some shrubs bloom only on the previous season’s growth. For example, forsythia, lilac and spirea fit into this group. If you want them to rebloom the following season, you should complete the pruning immediately after the blooming period is over. Pruning these shrubs while still dormant in early spring removes potential flowering branches for the growing season.

Often times shrubs are completely overlooked until we notice they have out-grown themselves. These can be reduced in size or re-shaped by pruning and thinning over a three to four year period. Often we do not have this kind of patience. So, many folks cut everything back to four inch stubs. The result will be a flush of growth that will be vigorous and full.

Summer flowering shrubs such as mock orange and potentilla that bloom on growth produced earlier in the growing season will benefit from some renewed pruning, giving them a flush of flowers in late summer.

Evergreens generally have a longer pruning season than deciduous plants. In addition to early spring and midsummer, pruning after new growth has hardened is acceptable for pines and spruce. Junipers and arborvitae can be pruned up to mid-August.

Often Mother Nature does her own pruning but the results are not pretty. To clean-up the tree and remove the damaged branch, go ahead and prune even though it may not be the optimum time.

Pruning of fruit trees should be done annually. I suggest removing the small branches which grow inward. These are the ones that create dense growth reducing air circulation and sunlight. Also, they tend to rub against other desirable branches causing wounds and possible invasion of unwanted bacterial and fungus organisms.

All woody landscape plants will need pruning during their lifetime. The objectives of pruning are to produce strong, healthy and aesthetically attractive plants that complement our property. You can achieve these objectives by gaining an understanding of why, how and when to prune, as well as a few basic principles. This can be done by requesting a new and free NDSU Extension publication called “Basic Guidelines for Pruning Trees and Shrubs” from the Williams County Extension Office at 701-577-4595.