TREE AND SHRUBSLeaf it to me

Terror Free Tree Trimming

Terror Free Tree Trimming                             by Connie Kratzke

This article was originally written for “The Glencoe Enterprise” newspaper.  My column is entitled “The Hort Report.

Many folks get squeamish at the thought of hacking limbs from their trees with menacing tools.  They wonder how to achieve scalpel-like precision with jagged-toothed saws.  However, unlike our appendages, tree limbs grow back.  There is some room for error during the learning process.  Once you know a few, simple rules; you can avoid causing any permanent disfigurement. 

First of all, it is best to avoid pruning most trees from the middle of April through the middle of July.  Oak Wilt is a potentially fatal fungus that wreaks its havoc between April and June.  Sap Beetles are drawn to spores that are produced within the wood of deceased oak victims.  Since the spores and the beetles are on the same page at the same time, the fungus is easily spread.  Pruning oaks during this time frame is like holding the door open for the dirty little beetles.  Honeylocusts can fall victim to Nectria Canker.  This insidious fungus creates lesions on the trunks and branches of infected trees.  These sores can eventually girdle and kill the trees, by blocking their flow of water and nutrients.  Cankers also create weak spots that break easily during storms.  The guilty fungus that causes these problems loves damp weather, whenever it occurs.  Maples trees can also be affected.  Maples, birches, walnuts and a few of their relatives have a tendency to ooze a lot of juice when you prune them after their sap begins to flow.  While this doesn’t cause them any harm, it is messy and easy to avoid.  People start tapping their maple trees in mid-February, so you might want to fall prune these sappy types.  As if that weren’t enough to worry about, apples and their family members can contract Fire Blight when conditions are warm and wet.  This bacterial disease becomes active as the temperatures warm in spring.  Infected plants secrete sweet, sticky, bacteria-filled stuff.   This attracts droves of well-intended insects.  These insects travel from tree to tree, happily collecting pollen without ever knowing that they are leaving hitchhikers behind.  Mountain Ash seem to be especially susceptible to this problem.  That about does it for the devastating plagues of spring!  Sometimes, Mother Nature forces people to trim their trees during risky periods.  Pruning sealer or latex paint can be used to seal the wounds when this occurs.  Avoid using sealers at other times, as they actually prevent the cuts from healing over.   

All of this probably seems pretty confusing.  Don’t worry, it gets better.  There are still a couple of prime pruning weeks left.  This is a great time of year to prune apple trees.  Every year, I prune my apples in March or early April.  Most trees can be pruned from mid-February through early April.  Spring bloomers may lose a few flower buds, but are less vulnerable to disease during dormancy.  This year, our horticultural hibernation period has been particularly long; which buys us a little more time.  Trees grow very rapidly right after they wake from their winter slumber.  Therefore, the pruning cuts heal over quickly.  Early spring is usually a comfortable time to be outside working.  Best of all, the trees are completely naked.  This allows you to clearly see their branching structure.  Leaf free tree debris is less bulky and easier to clean up too.

Probably the most important thing to learn is where to disconnect each branch.  A special bunch of rapidly dividing cells is located just beyond each branch/trunk and twig/branch junction.  These cells help pruning wounds heal quickly, with minimal scarring.  Open wounds are portals for insects and pathogens; so the faster they heal, the better.   When a cut is made flush with the main branch or trunk, the do-gooder nurse cells end up in the brush pile and the tree is left to fend for itself.  Donut-like scars often result from the tree’s inability to heal completely without its helpers. These eye-sores serve as permanent reminders of each wrong-doing.  Luckily, this can be avoided.  Study each intersection where you plan to make a cut.  Look for faint ridges in the bark that create slight swellings where each branch connects to its support.  When you cut just outside of this area, you should be cutting at a slight angle.  Look closely at the palm of your hand.  There is a diagonal crease where your thumb is attached.  Branches are connected in much the same way.  To get a feel for where you should make your cuts, you can practice on some buckthorn.  Chances are, if you don’t have any; your friends and neighbors will be happy to let you cut up theirs.  The point is, you should get used to identifying “branch collars” before you work on anything you care about.  Dissecting large, twiggy branches from the brush pile is another harmless way to get acquainted with the process.

When it comes to which branches you should cut, start with the obvious.  Remove all broken, diseased and damaged branches.  Limbs that look like they may have been attacked by fungus or disease should be handled with care.  Sterilize your cutting tool between cuts with a 1:9 ratio of bleach to water.  Plums, cherries and apricots are vulnerable to black knot fungus.  Trees that look like they have been defecated on by dogs are victims of this pest.  These trees should be pruned when they are completely dormant; in late February here in south western Minnesota.  Cuts should be made at least six-inches behind each black gall.  This ensures that the fungus is being removed and not redistributed.   

After you get all of the ominous stuff off, look for suckers and water sprouts.  Suckers are shoots that pop up right next to the trunk.  Ideally, these should be removed by grabbing them at the base, and pulling upward with a twisting motion.  This is only possible, however, when they are quite small.  Severing them off just below the soil line is a good alternative.  Doing so prevents them from growing back with a vengeance.  Water sprouts are twigs that grow perpendicular to their branches, often in an upward direction.  Ninety-degree angles are undesirable in arborculture, because they are vulnerable to breakage.  Get rid of all of the water sprouts that you see. 

Next, look for branches that grow inwards towards the trunk.  These individuals block air from moving through the tree, increasing the risk of fungal attack.  Also look for branches that cross or rub against each other.  Try to remove the trouble maker and leave the branch that seems to follow the tree’s natural growth habit behind. 

Whenever if can be avoided, try not to remove branches that are thicker than your thumb.  Smaller wounds heal more quickly.  Branches that are less than a half inch in diameter can be removed with a good-quality bypass pruner, like a Felco.  Loppers work well for branches that are up to about an inch in diameter.  That is probably pushing it.  Anything larger than that should be removed with a pruning saw.  Curved saws work quite well.  Such larger branches should be removed through a process of a few, separate cuts.  The first cut is always made from the top of the branch downward, several inches ahead of where the final cut will be.  The second cut is made from the underside, upward; about one inch behind the first cut.  Finally, the cut that gets the job done is made, just outside of the branch collar.  Following this process ensures that the limb doesn’t tear off before it is completely cut through.       

That about does it!  Pruning is complex to describe, but not that difficult to do.  Like riding a bike, once you get a feel for it; you are good to go forever.  Practice on rapid growers or invasive species.  Study plants and look for branches that break the rules.  This will help you see their natural growth habit and envision the final result. 

About the Author

Connie Kratzke is a MNLA (Minnesota Nursery and Landscape Association) Certified Professional and a MnDOT (Minnesota Department of Transportation) Certified Landscape Specialist.  She has worked for Kahnke Brothers, Inc., in horticulture for nine years.  During this period, she has attended many industry seminars on horticultural topics for continuing education credits.  Previous to her career in horticulture, she was a member of the Carver/Scott County Master Gardeners.

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