With winter comes high winds, snow and ice loading. This should be a concern for tree owners. Reduction pruning is one remedy for these environmental stresses. I’ve been re-reading some great literature on the University of Florida’s website (http://hort.ifas.ufl.edu/woody/reducing-damage.shtml) on how the reduction of mature trees can play a major role in aiding the biomechanics of a tree.

Reducing trees is tricky business, but with the proper dosage and timing, tree reduction can really mitigate the overall leverage forces experienced by trees. There is a cost though, when considering the specific size of pruning cuts.

Small pruning doses will be easier for trees to handle, especially mature trees. Also, consider ‘portion reduction’ (UF Website) in which you only deal with very specific areas of the crown, say one or two major scaffold limbs every pruning cycle, until reaching the desired goal. This could be a several year process, so it will need commitment not only from the tree owner but the arborist as well. On the budget end of business, planning and breaking up doses will be easier to handle for the client as well.

“Reduction is a balance between accomplishing objectives such as reducing failure potential and managing defects behind pruning cuts created by the treatment ” (http://hort.ifas.ufl.edu/woody/philosophy.shtml).

What are the objectives? I think this may be one of the first things I ever learned about pruning: ask why? What is the purpose of the treatment? In large trees I think many times the answer is to prevent failure, especially when there are unmovable targets present. And size. In our local market, people are infatuated with making trees smaller. I’m sure this is true in many other places of the world. Controlling the size of a tree will always be in high demand. The good thing about reducing a tree’s size, when it’s managed correctly, is that it does directly reduce the risk of failure. That’s a good investment, especially in an area with harsh weather factors like those that a deep winter brings.

But there is no formula, really. The prescription for reduction relies on many factors. Consider: species, location, pruning history (health/disease/IPM history) budget, access, targets and overall aesthetics. Also, remember that every pruning cut administered causes a wound which takes energy to heal. This is a major expense for the tree, and may become even more a part of the management plan than tree size.

“Reduction should be applied only after considering the long term treatment, monitoring, and commitment associated with this method of pruning” (http://hort.ifas.ufl.edu/woody/philosophy.shtml)

The cost for making large cuts can be high. No pun intended.

“With large pruning doses, these defects can include cracks and decay in pruned branches and dead bark on retained branches from sudden sun exposure; these defects can be very damaging to trees” (http://hort.ifas.ufl.edu/woody/philosophy.shtml).

My question is, how can we define a large pruning cut? A small pruning cut? How do we communicate it to tree owners? It must be in the form of a ratio (*aspect ratio, which Ed Gilman also describes in his research) which I’ll save for another piece. But consider this link also provided on the UF website for a quick visual aid of trees properly reduced:

http://hort.ifas.ufl.edu/woody/rcs-app-reduct.shtml

Also try to define a maximum dosage line for each pruning cycle. When coupled with a other prescriptions such as thinning, it can be easy to cross the threshold of what the tree can handle as well.

“…It is easy to administer an excessive pruning dose when combining pruning methods, especially when applying them to the entire tree. Trees pruned in this manner become stressed because they lose storage capacity and access to energy reserves in the wood, can form cracks in wood, and may begin decaying internally while showing no outward signs. Hardwoods pruned in this manner typically sprout aggressively, quickly filling voids” (http://hort.ifas.ufl.edu/woody/philosophy.shtml).

Consider this research from Ed Gilman on the effects of high winds on trees pruned and not pruned:

http://hort.ifas.ufl.edu/woody/wind-research.shtml

Of course reduction isn’t for every tree, or every arborist out there. But don’t go around saying size don’t matter.