3 rules of pruning

Following the why, when and how theory keeps plants lush and lovely

Arkansas Democrat-Gazette 3 rules of pruning Illustration
Arkansas Democrat-Gazette 3 rules of pruning Illustration

Pruning plants in the landscape can be a daunting task.

"How far back should they be pruned," "when should I prune" and "how do I prune" are frequent questions all county extension agents get.

Pruning can be surprisingly simple if you can answer those three basic questions.

WHY

Having a reason to prune is the first thing. Has the plant grown too large, is there diseased or damaged wood, does the plant need to be pruned to increase flowering or open it up to sunlight or increase fruit set?

Are branches hitting the roof of the house, brushing your car every time you back out of your garage or blocking visibility of pedestrians or traffic?

Are branches crossing through the plant or rubbing up against other branches, thus wounding both?

And last, do you like your plants in perfect round balls or boxes, or in spiral or topiary forms?

These are all reasons why. Some better than others.

Once you know why you are pruning, determine the time you should prune. Chances are you planted a flowering tree or shrub with hopes of having flowers. When a plant blooms determines when it should be pruned.

Plants that flower in the spring should be pruned as soon after flowering as possible, but no later than June 15.

Spring-blooming plants, starting with camellias and ending with mock orange (and including azaleas, forsythia, flowering quince and many more) set flower buds at the end of summer into early fall.

We want to give these plants a chance to bounce back after pruning. Typically, after the middle of June, temperatures are going up and we get less rain. We don't see rapid new growth in the hot summer.

Although there are a few exceptions (notably big leaf hydrangeas, oakleaf hydrangeas and gardenias) shrubs and trees that flower in the summer are blooming on the current season's growth. They should be pruned between the end of February and mid-March.

This year, our mild winter has put most plants a good two to three weeks ahead of schedule. Roses, buddleia (butterfly bush) and crape myrtles are all leafed out or almost there.

If you have not pruned roses or butterfly bushes, you really need to, or you won't have as many blooms this summer. While annual pruning is not needed on all shrubs, roses, buddleia and summer-blooming spirea do benefit from a severe haircut every year in late winter. If left unpruned, the stems grow woodier and you will only see blooms on the tips of the branches.

Pruning after plants are fully leafed out is not going to hurt the plants, but it can delay the first blooms. Losing a few early blooms is preferable to having a gangly, less productive plant all growing season.

NEVER

Crape myrtles do not need to be pruned every year, unless they are dwarf plants or young ones that have not developed their shape yet. They should never be pruned back to those ugly knobs each year, which is known as "crape murder."

We see too many examples of butchered crape myrtles all over the South.

Know the mature size of the plant you are buying. There are dwarf forms, from groundcover size to those that will be 3 to 5 feet tall at maturity, all the way up to trees 30 feet tall. If you are growing a standard crape myrtle, let it become the tree it was meant to be. Once you have it shaped, minimal pruning is all that is ever needed.

Big leaf hydrangeas, oakleaf hydrangeas and gardenias don't follow the rules. These plants all bloom in the summer, but they set their flower buds at the end of the summer into early fall. If you prune them before growth begins, you will not have flowers this summer. The time to prune them is when the flowers begin to fade.

Again, only prune if there is a need.

Two other members of the hydrangea family are panicle and smooth hydrangeas, which include "Limelight" and "Annabelle" types. These varieties bloom on the new growth and thus can be pruned in late February to mid-March without damaging flowers. Prune as little or as much as you want it to grow.

Shrubs that you are growing primarily for foliage -- hollies, cleyera, boxwood and elaeagnus -- can be pruned lightly at any season. If you plan to remove more than a third of the plant, then try to get this severe pruning done between February and mid-April to allow recovery time.

HOW

There are various forms of plant growth. Some shrubs have a main trunk that comes from the ground and from which all the branches grow. Other shrubs have multiple trunks, known as canes, with none being the most dominant or main trunk.

Cane-producing shrubs: These include hydrangeas, nandina, spirea, abelia, buddleia, itea, forsythia and red and yellow twigged dogwoods.

If you need to prune these plants you remove the older, woodier canes at the soil line. This is known as rejuvenation pruning. Cutting out the less productive stems will encourage new and vibrant growth to come from the ground up.

Forsythia will bloom better if you remove a third of the old canes every year after bloom. The older and woodier the plant gets, the fewer flowers you see.

For some cane-producing plants, we do a combination of thinning and cutting back from the top. Buddleia and summer spirea benefit from shearing and thinning to keep them blooming. You can remove some of the thicker, woodier stems at soil level and then shear the rest of the plant back to keep it full and low to the ground.

If you are growing a taller variety of buddleia, you can prune less severely, but take it back by at least half.

If you are pruning cane-producing plants, the timing depends on when each type of plant blooms.

For instance, red and yellow twigged dogwoods are grown for their bright red or yellow stems in the winter. As growth begins in the spring and they leaf out, they are just another plant in the garden. The winter stems are more vibrant on young stems. The older and woodier the stems, the less red or yellow they are. Removing a third of the canes each spring will keep them prettier in the winter months.

Dominant trunk: Plants with a dominant trunk include azaleas, hollies, magnolias, camellias, boxwood, juniper and cleyera. If they need pruning, there are two methods.

The preferred method is selective thinning, where you remove specific branches to a node. You can actually aim the new growth by pruning to a bud facing that direction.

These plants can also be pruned or sheared as hedges, but the resulting new growth will all be at the same level and so will most of the blooms. Selective thinning gives shrubs a fuller and more natural look than the "meatball" forms. Again, timing is based on bloom time.

True hedges that are grown as a living fence should be pruned with hedge trimmers. Try to keep the top angle of the hedge slightly narrower than the bottom of the hedge to allow sunlight to reach the entire profile of the plant. If we make the top too wide, it shades out the base, which can reduce leaves down low.

TOOLS MATTER

Now that you know why, when and how, make sure that you have the proper tools to do the job.

Fit the size of the pruning tool to the job being done. Some plants can be pruned with hand pruners, while others need loppers, pruning saws or even chain saws.

A nice clean cut is the best approach, and sharp tools make that happen.

Tree paints or wound dressings are not needed. If you are working in diseased plants, consider sterilizing your tools between pruning cuts or you will spread the diseases.

Plan your expected outcomes, prune a little and evaluate. You can always take off a few more branches if needed.

And if you have questions, call your local University of Arkansas Cooperative Extension Service county office.

Janet B. Carson is a horticulture specialist for the University of Arkansas Cooperative Extension Service.

HomeStyle on 03/18/2017