Pruning with Purpose

Garden Spot

Removing dying leaves helps the plant both aesthetically and ensures better health. Photo: Derek Thomas

Our beloved gardens of Capitol Hill are often gardens in miniature. We find smaller varieties of favorite plants due largely to the space limitations our properties present. Many Hill gardeners can be seen frantically pruning unruly plants in an attempt to contain some of the larger specimens within limited space. Enter the art of pruning-- a complex cutting of the branches and leaves of our plants and trees. What follows is a broad overview of the craft; any attempt I make here to fully cover the topic of pruning will need more pages that this column allows. What I want to do is challenge each one of you to go out and get a good book on pruning so before you start to chop off life and limb of your plants, you are armed with the understanding of why.

To prune or not to prune

One of the primary reasons for pruning is to make sure that plants are as healthy as possible. Removing weak and damaged limbs and reducing the risk of disease and infection are two of the accomplishments proper and timely pruning achieves. Pruning will also increase a plant’s ornamental value, and improve their natural appearance.

You have to understand the principals of a plant’s response to pruning in order to fully realize its full potential. Understanding how plants grow will aid you in comprehension of the how and why pruning should be done. Pruning should never be done without a good reason or without a clear purpose. You should have a clear idea of the intention of each pruning cut you make.

Why pruning works

The most important thing to know about pruning is that when a part of a plant is removed you are diverting hormones. Plants have growth regulating hormones that ensure that the tips continue to grow away from the roots, a phenomenon termed “apical dominance.” When you remove these young green shoots, the plant will have to divert its growth hormone known as auxin to the next highest node, a node is usually located in the space where the leaf connects to the stem. Most plants will respond with new growth at the node closest to the cut you make. Some plants will respond to this type of pruning by producing multiple stems along nodes below the cut. Each plant has different requirements when pruning. Knowing the growing habits of the plant will help you to properly prune. Pruning also ensures vigorous new growth while keep dead and decaying limbs from spreading disease and infection to younger healthier limbs.

Controlling plant size

Heavy pruning can be used to control plant size. When heavy pruning is done there is usually a flush of new growth that follows. The pruning has stimulated new growth, however you have also cut the plant’s ability to produce food (photosynthesis), while forcing the plant to use up its stored food. Keep in mind repeated heavy pruning without proper fertilizer will actually hurt the plant in the long term. So it is important to use heavy pruning sparingly. If your plant continues to exceed the space allowed perhaps it is best to eliminate the plant and replace it with a smaller variety.

When to prune

It is important to understand the habits of the plant you are about to prune. If you are thinking about pruning your Hydrangea back to the ground this spring, be prepared to have sparse, if any, blooms this year. You see, most Hydrangeas only bloom on last year’s stems and pruning them back to stubs in early spring will produce wonderful leaves and very few, if any, blooms. Always be careful when pruning in early spring since this is the time that food reserves are moving rapidly back up the stems and cutting back harshly in early spring can severely hurt the plant. This problem can be avoided by pruning in late winter or once the plant has fully leafed out. Try to avoid heavy pruning in the middle of summer as this can harm the plant. Pruning deciduous trees in winter allows you to see the structure of the tree without the obstruction of its leaves. Winter pruning also helps prevent the entry of pathogens, since healing will be rapid in spring.

How to prune

Once you know the time is right for your particular plant, and you know the parts that will be removed, you must now consider performing the job in a way to insure rapid healing with minimal risk of infection. The cuts must be made cleanly, with no crushing or fraying of twigs. This requires that you use tools that are suitable for the pruning task at hand. This is where referring to a good pruning book will be particularly helpful. You should prune above a bud that is the right height for the desired outcome. Make sure that the uppermost bud is pointing in the direction that is desired. Make an upwardly sloping cut starting on the opposite side of the shoot to the bud. Cutting on an angle will ensure water runs off the new cut. Refrain from using pruning seals since their benefits have not been proven. In fact many professionals are doubtful that there is any value in using these products.

Depending on the type of pruning you are planning on doing there are many products on the market. Make sure that you purchase tools from a company that is well respected. Buying discount pruning tools will produce discounted results. When buying your pruning tools make sure you buy a reputable brand, keep your tools sharpened, and clean and your plants will respond in a healthy manner.

The final cut

I hope this overview has inspired you to do more research in this area of gardening. Keep in mind that proper pruning is a must to plant health. Proper tools and knowledge of pruning techniques will take you far in this very important, often discounted area of plant maintenance.

Derek Thomas is principal of Thomas Landscapes. His garden designs have been featured on HGTV’s Curb Appeal, and Get It Sold. His weekly garden segment can be seen on WTTG/Fox 5 in Washington. He can be reached at www.thomaslandscapes.com or 301.642.5182.

You can find and friend us on Facebook at Facebook/Thomas Landscapes.

Follow us on Twitter @ThomasGardenGuy For Great Garden Tips.


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