If pruning is necessary, you can do light, corrective pruning any time of the year. More severe pruning of most deciduous trees and non-blooming shrubs should be done during their dormancy in the late winter to early spring before they leaf out. Insects and disease spores are less likely to infest pruning cuts during this time. This is especially important for fruit trees that are vulnerable to fireblight. It is also easier to see the plant’s form when it is without leaves. In spring to early summer, energy reserves are being used for new growth and heavy pruning can weaken a tree or shrub. By late summer and early fall, plants begin storing their energy reserves in their roots to use in dormancy for next season’s spring growth. Pruning should be limited during this time since it may encourage new growth that would not have time to mature before being subjected to freezing temperatures. By late fall after they have lost their leaves and there have been several hard freezes, more of the energy reserves are in their roots and there is less stress on the plant.
Spring-flowering shrubs bloom on the previous year’s growth. Flower buds develop in midsummer through fall so pruning in the fall and winter removes the coming year’s flower buds. If you thin right after bloom before the flower buds are set you will maximize the next season’s flowers.
Spring-flowering shrubs include Forsythia, Nanking Cherry, Quince, Bridalwreath and Vanhoutte Spireas, Viburnums, Beautybush, Lilac, Peashrub and Weigela. It is recommended that you deadhead the faded flowers after they bloom. This not only makes the plant look tidier but conserves its energy for seed development.
Summer-flowering shrubs bloom on new wood that grew earlier in the current growing season. Flower buds develop in midspring through midsummer so pruning during this period removes the season’s flower buds. If you thin right after bloom before the flower buds are set you will maximize the next season’s flowers. Removing older canes of flowering shrubs also allows better sunlight penetration which results in better flowering throughout the shrub instead of just at the top. Summer-flowering shrubs include most Butterfly Bush, Blue Mist Spirea, Hancock Coralberry, Mockorange, Potentilla, Japanese Spirea, Annabelle and Peegee Hydrangea, and Althea/ Rose of Sharon.
Pruning Techniques – To Be Continued
About Urban Gardens, Inc.
Urban Gardens provides landscape design and consulting services to residential clients whose projects range from historic renovations to new subdivisions with a blank slate. Sarah Christian owns and operates Urban Gardens in the internationally recognized Stapleton Development in Denver, Colorado. She received her Masters degree in Landscape Architecture from the University of Colorado at Denver in 1995 and has worked in Colorado since that time. She is licensed by the state of Colorado and is a member of the American Society of Landscape Architects. You can visit her web page at www.urbangardensinc.com