When to Prune?

If one were to pick the most repetitively asked question in the gardening industry it would probably be, "When do you prune?". The answer can vary widely depending on the specific situation and plant in question. In general the best time to prune any woody plant is just before new growth starts in the spring. For the Ithaca area the time is somewhere between February and the end of April.

Plants are most actively growing and producing food during the summer. As days become shorter in late summer growth slows and sugars accumulate in the leaves. Before foliage falls food moves from leaves into branches and eventually roots as the formant season sets in. Because of this, early spring pruning won't disturb much needed energy reserves. Added benefits are wounds that heal quicker and a more visible branching structure, as well as a schedule free of later season tasks.

There are cases in which pruning should be done during the growing season. If trees or shrubs flower on wood produced the previous season, they should be pruned after they flower or you run the risk of cutting off the yet to be blooms. Some plants that fall into this category are: Forsythia, Crabapple, Quince, Bigleaf Hydrangea, Beautyhbush, Magnolia, Weigela, Rhododendron, Japanese Andromeda, Mountain Laurel, and some Spireas. Summer pruning the vigorous growth of an immature fruit tree can re-direct energy into fruiting. Summer pruning is also fine for a tree or shrub that has reached a desired size or needs to have a structural problem fixed. Some trees will bleed profusely such as Scholar Tree, Golden Chain Tree, Dogwood, and Yellowood if pruned in spring. Prune these bleeders in the dormant season or mid summer.

Pines should be pruned after the candles elongate but before the new needles expand. Candles are the candle-like new growth that pines produce in the spring. Cutting them back will produce a densely branched tree.

The worst time to do any extensive pruning is right after leaves emerge in the spring. This is because stored energy has been used to power the expansion of new foliage, yet the foliage has not begun producing enough food to replenish the supply. Until food production equals use, the plant can't afford to loose foliage.

Determining when to prune is really a matter of understanding what is going on in a plant at the time. When will foliage loss be least detrimental, when will the plant heal the fastest, what is the extent of the pruning needed, are some of the questions that should come to mind first. Following some of these basic rules will lead to a more vigorous, healthier plant in the long run.