Tree Pruning Explained
TREE PRUNING EXPLAINED – (Randy McManus, CLP  –  Willamette Landscape Services, Inc.)
Good pruning is often important for extending the useful life of landscape trees.  With a basic understanding of pruning do’s & don’ts, a little winter work can be applied to accomplish an overall reduction in size or spread when necessitated by space limitations.  Additionally, the removal of weak branches, & the thinning of densely-branched tree crowns reduces winter storm damage & improves light penetration & air circulation. 

In order to understand how to accomplish your pruning goal, it is important to visualize how the tree is going to respond when it begins growing again next season.  Any tree will almost always respond with at least two shoots from just below your cut if you prune a twig or branch anywhere along mid-stem.  This would only contribute to the tree becoming thicker & more shrub-like.  Therefore, you will almost always want to locate pruning cuts either where the branch/twig originates, or just above a set of existing lateral branches that you want to take the tree back to.  This way you’ll keep a more open, natural form.

Select branches that grow at 30-45 degrees from horizontal for a strong branch structure. Remove all other limbs that crowd the most desirable “keepers”.  You want to create a little open space around each remaining branch.  Remove dead twigs, then finish with a minimum amount of shaping (applying the above-described principles.)

Make pruning cuts flush (little or no stub) when using hand pruners.  Branches large enough to require lopper work or saw cuts usually have a small swelling at the base that should be left on the tree to speed healing.

When sawing a medium to large branch you run the risk of having the branch fall & tear additional bark & wood as you cut.  To avoid this, remove the branch in stages so that you will just have a short 6-12″ stub to remove with a final cut.

For ladder work, use only three-legged “orchard” ladders for stability on uneven surfaces.  Do not use a stepladder because of the instability of four legs in almost any location where trees are found.

Sharp tools are very important, both for making the job easier & for minimizing damage to the tree.  Loppers & hand pruners are designed to be sharpened on only one side of the blade.  This is accomplished quickly & easily with the use of a simple hand file that should be kept handy for occasional touch-ups.

Winter is the best time to do this work simply because it is so much easier to see what you have to work with when the leaves are gone.  One possible drawback however, is that new spring growth may be even more vigorous than before.  Remember, the same root system is still there to feed a now-reduced crown. 

Mid to late summer can be a good time to prune in order to minimize future growth.  With the spring flush of new growth past, reducing the amount of foliage at this time of year also reduces “food” production & storage for next year.