What is the opinion of maple experts on the timing of pruning of maples? I have heard that pruning in the Pacific Northwest during the months of February and March ,before bud break, may promote disease. Do pruning cuts, in these months of many rainy days, allow more disease to enter the trees vascular system than in the drier days of June-August? Has any theory on pruning timing been backed up by reaearch or is most advice personal experience?
tonyp, The preference is yours. For me, I like to prune in summer as the cuts heal much faster. Additionally, here in southern Oregon, the hot valley that I live in gives us and extended growing season and we typically see lots of summer growth here or what many call the second flush of growth that some/most/many maples will send out. If we prune in July or early August, we can see soem redirected growth occur for us and this is very helpful if we have some goal in mind for out pruning. The other side of the arguement seems to be, if you know you are going to remove the wood anyway, why let the tree waste energy on it during the growing season when you can just remove it when the tree is dormant. Also, many feel that pruning in the hot part of the summer puts undue stress on the plant. I myself, do not subscribe to either of these ideas as a standfast or better rule than summer pruning. If the cut heals faster in the summer, then it makes the most sense to me to prune then. Any open wound is a means of entrance for disease and as you said, rains following the pruning do not do us any favors. I am most in-favor of late season pruning--or year around light grooming.
In the PNW, you can prune in winter and spring, but it is best to prune when you are assured of 2-3 days of dry weather following your cuts to allow callusing of the wounds before rain.
Fall and winter is a common time to prune and shape deciduous trees and shrubs . Exceptions to this are maples which will bleed or ooze sap unless pruned when in leaf. When maples are pruned in late winter or early spring the wounds flow with sap. If heavy sap flow occurs, pruning should be delayed until midsummer. This flow of sap can lead to disease invasion and weakening of the tree. The preferred time to prune maples is between mid-July and August, a period when sap won't run from cuts. The one time when trees should not be pruned is during early spring when buds are breaking during leaf expansion. Maples should be given a thorough pruning every three years and minor "touch up" pruning annually. A thorough pruning involves removing dead limbs, crossing branches (or branches that will cross in the future). Give newly planted trees and shrubs only minimal pruning. Removing too much top affects the production of food energy (carbohydrates) and can result in poor root development. After planting, prune out broken branches and those with weak or narrow crotches. With young trees, leave some of the lower limbs and sprouts even though they will be removed later. These limbs provide the closest source of food energy for root development. I have also found that trees will form a stronger trunk if the lower branches are not trimmed for a few years.
