Tree Pruning Pointers

You’ve sharpened your pruning shears, polished your loppers, and gassed up your chainsaw.  Your trees need to lighten their woody load and you’re the person to help them do it.  But hold on a moment!  Before you start cutting keep the following pointers in mind:

  • When you cut can matter as much as what you cut.
    • Evergreens are usually recommended to be pruned in late spring.
    • For many deciduous trees it can be beneficial to prune after it has dropped its leaves in late fall or winter. 
    • Not only will you see the structure of the tree more clearly, the tree isn’t being deprived of the foliage it worked so hard to make earlier in the season.
    • If your tree is spring flowering (flowering plum, flowering pear, etc.) you may want to wait until after it flowers in the spring because of the impact on your floral display. 
  • Know your three “D’s”.  If the wood is dead, diseased, or damaged it’s an easy candidate for removal.
  • If branches touches your home they should probably go.  Trees can damage your home over time with continued contact; prune branches away from structures to coerce the tree into growing elsewhere.
  • Limit pruning to 20% or less of foliated healthy wood per year.  Sure you may want to hack that overgrown Maple with reckless abandon, but you’re severely impacting the tree’s health when doing so.  Pruning can be a process that takes more than one season–especially if mature trees have gone untouched for years at a time.
  • If a branch touches a powerline THEN THAT BRANCH IS OFF-LIMITS.  Sorry for the caps lock there but I can’t stress it enough.  You don’t want to make yourself into a lightning rod by accidentally making contact with the line; contact your public utility instead.
  • Prune just outside the branch bark collar and branch bark ridge.  Trees naturally shed branches quite well on their own, and you should try your best to prune in the same manner nature gets it done.  The branch bark collar is a subtle “flaring” on the bottom of the branch where it meets the trunk, and the branch bark ridge is a line that runs perpendicular to the branch (pictured below left).  You can frequently tell when it’s done right based on how the tree heals (e.g., the “donut” pictured below right).
  • The 1/3 rule applies to lateral branch pruning.  You don’t have to remove the whole branch when pruning.  The branch can be brought back to a lateral branch as long as it is at least 1/3 the size of the branch you’re removing.  The “X” branch is not a suitable size but the “O” is (picture below).
  • If you are cutting a large branch, make an undercut first (example below).  An undercut will help protect your tree from peeling as the branch comes down. Head 12″-18″ out from the branch bark collar, make your undercut (1/3 the width of the branch usually does the trick but you can go to 1/2), then cut to the right of your undercut (away from the trunk).  Once the branch is down make sure to remove the remaining stub using the branch bark collar/ridge as your guide.
  • Don’t top your trees.  Just don’t do it.  There are methods that appear to be topping at first glance (such as pollarding) that require professional experience to be done correctly.  Contact an ISA Certified Arborist to find out more if you’re interested.

While this isn’t an exhaustive list of pruning methods it’s a good start, and with a little practice you’ll be comfortably pruning your landscape trees in no time.  The University of Nevada, Reno Extension offers many kinds of horticultural classes if you’re ever interested in deep diving pruning among many other topics.  Make sure to check this site often to see what’s coming up!

Chad Morris is the Commercial Horticulture Program Coordinator with the University of Nevada, Reno Extension.  You can reach him by email at chadmorris@unr.edu or phone, (775) 336-0249.  All in-text photographs taken by Chad Morris, banner picture provided by Wendy Hanson Mazet.