Pruning Trees and Other Perennials

Jesse Fulbright, MSU Liberty County Extension

I looked out our large picture window to the south the other day and realized it is that time of year again.  It is time to start outside yard work, specifically, pruning and getting trees and perennials in shape for the coming season.  Many of us know we need to prune but we don’t know why. 

According to the Montana Master Gardener Handbook, pruning can make a barren tree fruitful, bring overgrown plants back into bounds and can make a flowering plant bloom more profusely.  However, the catch is, it needs to be done properly.  Pruning is the removal of plant parts with a specific purpose in mind of changing the direction and amount of new plant growth, ultimately affecting the shape the plant.

For trees, pruning can best be explained by looking at what needs to be taken off first.  Look for signs such as water sprouts, those tiny branches coming out of the trunk or branches straight out.  Look for suckers near the base of the tree, crossed branches that will rub and injure the tree, dead branches, stubs of branches that weren’t properly trimmed before, and double leaders.  Double leaders are those branches that come to a fork and are more or less equally growing and forming two main stems.  You only want one main leader.  You never want to prune any more than about 1/4 to 1/3 of the tree’s canopy in one year, otherwise you take away its ability to capture nutrients.  Topping, hatracking, rounding or any other practice that decimates a tree, leaving it denuded is never an accepted tree pruning practice.  If your tree is like this, its life has been severely shortened and you might as well take the tree out for the bad that has occurred.

When thinking of pruning perennial shrubs or other plants in your yard and garden, you prune to promote plant health.  Eliminate dead, dying or diseased wood now before new growth occurs.  This is two-fold in purpose.  First, it is much easier to eliminate old tissue when you don’t have to trim around new tissue.  Secondly, if you have old, dead or diseased tissue, you want plant nutrients going to new tissue for vibrant and productive growth as well as disease suppression.  Pruning a thicker plant, such as a hedge also allows light to penetrate through the plant. 

If you have any questions about pruning, or feel hesitant about what to prune I would encourage you to contact your local county Extension office.

Now is the Time for Shrub Pruning

Kari Lewis, MSU Extension - Glacier County

Even though it hasn’t felt like spring much yet, the calendar says spring is right around the corner.  Now is the ideal time to prune many trees and shrubs as we commonly think of the late dormant season being when severe cold has passed, but new growth has not yet begun.  This dormant season pruning typically enhances the plant’s vigor, and will stimulate new growth.  In addition, pruning now will provide the trees and shrubs the entire growing season to recover.  This blog will focus on pruning shrubs, with information from the Montana Master Gardener Handbook.  

When a shrub flowers determines when is an appropriate time to prune that shrub.  Shrubs that bloom on current season’s growth which would be ok to prune now include Peegee hydrangea, potentilla, shrub rose, snowberry, and Hills of Snow bushes. 

One exception to pruning shrubs this time of year includes shrubs grown primarily for their flowers that that bloom in the spring.  Spring flowering shrubs are any shrubs that bloom at the same time or before the lilacs bloom.  These spring flowering shrubs bloom on LAST year’s growth, so should be pruned right after flowering.  Examples of these would be honeysuckle, rhododendron, lilac, and rambling rose bushes. 

Photo courtesy of Texas A&M Extension,
available at http://aggie-horticulture.tamu.edu/earthkind/
landscape/proper-pruning-techniques/

If you are wanting to prune shrubs into a hedge, small shrubs that are 1 to 3 years old should be cut back to about 3 to 5 inches above the ground to encourage growth of new shoots at the base.  If you have older shrubs that you would like to transition into a hedge, cut back one-third from their tops and sides to help develop a full, bushy hedge. 

The main thing to remember when pruning a hedge is that the ideal hedge is wider at the base than the top.  A hedge should look like a truncated cone shape. 

Often, I will see the exact opposite of this, that is, the top of the hedge is wider than the base.  This leads to thin, weak growth, as the wider top portion of the hedge shades the lower portion and without adequate sunlight to the lower portion of the hedge, it becomes less vigorous. 

Formal hedges should have one-third to one-fourth of their oldest branches near the ground cut back each year.  Upper branches of the hedge can also be cut back to their main parent stem to encourage fresh, new growth. 

If you prune any infected branches while pruning, make sure to clean your pruners with rubbing alcohol after each cut so that the pruners don’t transmit the disease to another portion of the hedge or to the tree you prune next. 

For questions on this topic, please contact Kari Lewis at kari.lewis@montana.edu.  Image courtesy of http://aggie-horticulture.tamu.edu/earthkind/landscape/proper-pruning-techniques/.