Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
February, 2009
Regional Report

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The 3-step method is a good way to remove a large branch without damaging the tree. Here, the first two cuts have been made; the final cut will remove the stub close to the raised branch collar.

Making Pruning Make Sense

As an Extension Horticulturist I have advised gardeners for a couple of decades now on various aspects of gardening. Many answers are simple and easy. Some are not. Pruning is one of those topics that although we try just doesn't lend itself to simple answers.

If you give a brief, "do this" set of instructions with a diagram of the often too perfect plant folks nod and head out to their landscape only to find themselves staring at their tree or shrub wondering where to begin. If you give a detailed explanation with instruction on plant responses to pruning and hormones that regulate growth (!) their eyes glaze over!

There are so many types of woody ornamental plants in our landscapes each with its own "best practices" when it comes to pruning. Evergreen hedges, conifers, deciduous spring bloomers, fruit trees, grape vines, newly planted trees, old trees that were never properly pruned -- well, you get the idea. One size doesn't fit all. Even with a particular plant such as a rose we have floribundas, hybrid teas, shrub roses, once blooming spring roses, climbers, and on it goes.

Alas we need not despair. This wonderful smorgasbord of woody plants need not leave us totally confused and afraid to prune lest we mess things up. There is a lot of help out there to guide us in learning how to prune. Books, Web sites, and free publications from your local Extension Office are all good places to begin. Knowledgeable local gardeners and experts at public gardens can provide hands-on demonstrations to guide you.

I think one of the best ways to start is with an understanding of some basic principles of plant growth. When we understand what effects our pruning practices have on plants we can better know what to do to get the plants to grow like we want.

Pruning cuts invigorate the plant to regrow near the point of the cut. Think of it this way, when you remove some of the top, the plants then will grow to restore the balance between its roots and above-ground portions. Some plants get older and less productive (blooms or fruit) in time. Pruning brings more fresh new growth to maintain productivity and attractiveness.

There are hormones produced in the end of a shoot that "flow" downward and suppress the buds along the shoot from growing. When you remove the end of the shoot you remove the source of these hormones and buds below the cut respond and take off growing. You can achieve a similar response by leaning a shoot out toward horizontal. This also reduces the flow of these hormones down the branch and buds along the shoot begin to sprout and grow. This technique is used in espalier fruit growing to manage and balance growth. It is also used with climbing roses to increase flowering all along a long lanky cane or shoot.

Plants that bloom in spring only set their buds in late summer for the next year's bloom. Winter pruning removes these buds. Thus winter pruning is okay for fruit trees that tend to set too much fruit, but not for once blooming roses, spirea, flowering quince, forsythia, and other plants grown for their gorgeous spring display. We prune those after they bloom to stimulate new growth which will then later set bloom buds on the new growth for an even better show the following year.

Heading Cuts and Thinning Cuts
One additional principle of pruning to keep in mind is the difference between a heading cut and a thinning cut. When you top off the end of a branch most plants will respond by sending several shoots out from below the cut. This is a heading cut and we refer to the resulting growth as a "crow's foot". Sometimes this is desirable, such as when our goal is to create a dense wall of foliage in a privacy hedge. Formal gardens are dependent on heading cuts to turn plants into geometric shapes like those spherical green "meatballs!"

However a heading cut -- and the resulting flush of shrubby growth -- often is not desirable when we are wanting to open up the interior of a fruit tree to allow more light in, or when we wish to leave a shrub with a beautiful natural form such as the arching shoots of a spirea.

A thinning cut on the other hand is made by cutting a shoot back to where it attaches to another shoot. This results in fewer new buds pushing out new growth near the point of the cut and instead directs the growth into the remaining branch. Thinning cuts open up a plant to more light in the interior and preserve the natural form of a plant.

The folks at the University of Georgia created a great online resource called Basic Principles of Pruning Woody Plants:
I suggest you check it out for a great introduction to how plants respond to pruning.

No matter how long I garden I find that there is something new to learn about pruning. While there is certainly a lot of science involved, it really comes down to an art and experience is a great teacher for us "forever students."

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