Pruning: the basics

This is an updated version of the plant care sheet that I give my customers, who often ask about how to best prune a variety of different plants. Feel free to copy it and keep it in a handy place!

Evergreens: Evergreens that grow continuously can be pruned or sheared anytime during the growing dwarfmugho.jpgseason (except late August, which can increase the risk of winter-burn). Plants in this category include: Junipers, Yews, Arborvitae, and Hemlock. If this is started early and done on a regular (2 times a year) basis, your plants will retain excellent form. Pine and Spruce normally put on a single flush of growth, then stop. If you are trying to maintain them at a specific size, (such as Mugo Pine), prune back 1/3 to 1/2 of the new growth (called candles) in early spring. Pruning of evergreen trees will be minimal, especially once they are established. Left photo: Dwarf Mugo Pine

Shrubs: Timing the pruning of flowering shrubs will depend on when they form their flower buds. Early-Spring flowering shrubs, (those that bloom on previous years wood, such as Azalea, Forsythia) shendsumhyd.jpgold be pruned immediately after flowering. This allows new flower buds to form for the following Spring. Mid-Spring-to-Summer flowering shrubs, (those that bloom on current year’s wood, such as Gold Flame Spirea, Hydrangea and Potentilla) should be pruned in early Spring and cut back 1/3 to 1/2 to keep them full. Shrubs not grown for their flowers can be pruned anytime, but an early Spring pruning before leaf-out allows the new growth to cover up the pruning cuts. Overgrown shrubs can be renewed by cutting 1/3 of the older branches to the ground (such as Red twig Dogwoods). Right photo: Endless Summer Hydrangea

Trees: Pruning can be done any time, but early spring is probably the best time. Look for crossing branches, diseased or dead wood, weak branch unions, suckers and water-sprouts,and overall aestheticcraprairiefire.jpg shape. EXCEPTIONS: Don’t prune Oaks (especially the Red oak genus) or Elms between early/mid April and July 1st. The risk of Oak Wilt and Dutch Elm disease is much greater at these times. Others to watch are Hawthorne, Mountain ash and apple trees, all three which can be susceptible to fire blight, especially if planted in a poorly drained soil. It would be a good idea to sterilize your pruning tool with a 10% chlorox solution between cuts.

Don’t worry if, when you prune your maple or birch, it starts bleeding (oozing sap). It may be unsightly, but it will not harm the tree.You can avoid this by waiting to prune until the leaves are full size. Don’t try to stop it with tree pruning paint. It won’t work!
Unless absolutely necessary, be careful not to top your tree. Topping will result in a flush of new growth and in the long run will be more unsightly than if you had done nothing.
Above photo: Prairie Fire Crab.

For more detailed info I recommend the following websites: The first is an excellent fact sheet put out by the University of Minnesota. The second resource is put out by the federal government that is a liitle more detailed with more pictures.