A few days ago a respected local gardening celebrity published an article cautioning her readers to skip winter pruning of trees because of potential freeze damage. There were many other good points made in the article but this piece of advice really stuck in my craw.
OK, full disclosure first: I'm an ISA certified arborist who also runs a full service landscape company. Why is this relevant? Mostly because of the seasonal aspect of how I make a living. My inspirational St. Crispin's Day speech for my crew this morning did little to change the fact that it was 18 degrees. When the ground takes on the characteristics of granite, tree pruning becomes our main source of work.
So my initial reaction to the article was something along the lines of this person is trying to steal bread from my child!
Deep breath.
Most arborists I know like to prune in the winter because the tree structure (or lack thereof) can be clearly seen without a cloak of leaves, making it easier to determine pruning decisions. Personal opinions aside, it is incumbent for an arborist to prune according to ANSI A300 pruning standards (the arborist's bible).This is what the guide has to say:
The best time to prune live branches depends on the desired results. Removal of dying, diseased, broken, rubbing, or dead limbs can be accomplished any time with little negative effect on the tree. Growth is maximized and defects are easier to see on deciduous trees if live-branch pruning is done in the winter before growth resumes in early spring. Pruning when trees are dormant can minimize the risk of pest problems associated with wounding and allows trees to take advantage of the full growing season to close and compartmentalize wounds. (Best Management Practices Tree Pruning Companion publication to the ANSI A300 Part 1: Tree, Shrub and other Woody Plant Maintenance-Standard Practices, Pruning, pg. 25 para. 1 &2)
For more info about winter pruning, check out these sites:
Trees Are Good
Chicago Botanic
Arbor Day
Minnesota DNR
Great info, including referencing ANSI and arboriculture reasoning! Those celebs...I moved partly because of a few. Yours seems nicer!
ReplyDeleteWhere I've run into trouble here (Albuquerque specifically) is late Feb / early March (very late winter) pruning on some species, such as desert willows and mesquites, to see them freeze back below most of the pruning cuts...those same branches got brittle within a couple weeks, then showed they were dead by not leafing out in April-May. Those were only pruned, assuming the trees were still deeply dormant (4-6 weeks until average last frost there), but maybe there's a cut-off date when that pruning stimulates growth, but where late freezes will hurt them? Maybe the species, or that particular year, too? Curious...
Great point. I wish more ASLAndians had your grasp and appreciation for the horticultural side of their craft.
DeleteNuance and regional consideration is important in any gardening/landscape discussion and perhaps I sacrificed both for the sake of trying to achieve clarity in the post. MOST hardwoods take winter and early spring pruning quite well, but ANSI does address sap dripping that can occur in some trees in the early spring (maples, birches, etc.), but this is merely an aesthetic consideration and has little effect on the health of the tree.
But back to your point- yes, I've seen the same kind of die-back on Chilopsis here, but I always took that as a sign of their "near-hardiness" in Boise. There are a handful of other trees I instinctively avoid live-pruning in the winter and early spring, including Honey Locust and deciduous flowering magnolias, although admittedly I've formed these opinions based on experience rather than empirical science.