Pruning in Minnesota

 

You don't need to create animals out of your shrubs to use good pruning techniques.

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Why prune?
Pruning is an art form for many.  Bonsai, espalier, and topiary all use pruning techniques to create beautiful works of art.  Bonsais known to be over 500 years old are still alive and on display today.  Trees ranging from apple to ginkgo are made into living fences through espalier technique.  Luckily, the average homeowner really just needs a few basic techniques to provide appropriate maintenance for their trees and shrubs.

Pruning helps maintain a healthy plant by removing dead wood from the tree or shrub. It can also prevent a plant from injuring itself from rubbing.  Pruning can also improve the aesthetics of a plant.  By pruning, gardeners can have a certain degree of control over the size and form of the plant.  Pruning can also encourage new growth and flowering.
  
When to prune
Pruning should be done on new shrubs and trees right away to remove dead wood.  Shaping of the plant can also begin right away.  Any branches growing inwards should be removed.  Branches can be removed to provide space for other branches.  Remember that the plant is going to get a lot bigger, so try to visualize what the branch will grow into.  As the plant grows, remove low growing branches to keep the crown high.

Winter can be the ideal time to prune most trees, as the tree is dormant and disease is also dormant.  Spring flowering shrubs can be pruned right after flowering.  Shrubs grown for their foliage should be pruned before the plant resumes growing in the spring.  As diseases become more of an issue, especially with trees, also be sure to find out the right time to prune first.  Some trees, like Oaks, can be extremely endangered if pruned at the wrong time of year.  Consult a local extension office if in doubt.

What tools to use
Pruning shears are a must have tool for gardeners.  These will work best for trimming smaller, younger branches.  Lopping shears and various saws can be used for larger branches.  Hedge shears can be used when trimming hedges, or for very small young branches. Always keep tools properly sharpened, as a sharp tool will make a cleaner cut, preventing damage to the plant.

Techniques
There are three major types of pruning: Crown thinning, raising, and reduction.

Crown Thinning: This is done to create an open tree canopy or shrub. Basically, you remove branches to imrove form and air circulation.  Any branches that are weak, too closely spaced, are rubbing, or are growing towards the tree should be removed.

Crown Raising: This is done to remove any low growing branches. On trees, this is generally done to lift the canopy higher to create space below. On shrubs, this can be done to alter the form or just to get branches off the ground, which can look poor.

Crown Reduction: This is done to control the height of a tree or shrub.  To reduce the height, the upright leaders are removed. Crown reduction can be damaging to a tree, and is probably best left to the professionals.

When shortening a branch, always cut above the bud that is growing in the direction you would like the branch to grow.  This bud will become the new leader on that branch.

When pruning larger branches, multiple cuts should be made to avoid damage to the tree.  The bulk of the branch should be removed before cutting all the way down to the branch collar, which should always be left intact. 

For more detailed information on pruning techniques and details on when to prune specific species, check out the sources below.

Sources:
University of Minnesota Extension Office
http://www.extension.umn.edu/distribution/horticulture/dg0628.html

Minnesota Department of Natural Resources
http://www.dnr.state.mn.us/fid/october98/10019808.html