Pruning refers to cutting a branch, stem or twig on a woody or herbaceous perennial. Pruning is usually performed to remove branches for safety, to prevent disease and decay, for shaping of growth and for increased growth and flowering. Of all the grooming techniques, pruning is the most important grooming technique to learn properly. In herbaceous perennials, bad pruning can be outgrown by the next season. However, bad and incorrect pruning can lead to long term problems, disfigurement and death of trees and shrubs.
Proper Planning and Design Lowers Maintenance
In a low maintenance landscape, plants are chosen for the desired mature shape and size and placed where they have plenty of room to achieve their mature growth. Ideally, then, we are able to appreciate the plant to its fullest.
Granted, it is hard to achieve the ideal in the landscape. Many times we fail to visualize how large a plant will get, especially when they are purchased in small containers. A new planted bed or border with shrubs that come in one gallon sized containers that will spread 6' x 8' tall at maturity looks sparse. So we naturally tend to plant them too close together, too close to buildings and directly under windows.
To combat our design flaw, we often substitute pruning to make the plan fit. Plants naturally grow to their mature height. Because of this, pruning to keep a plant's size in check is a repeating chore. If a plant is properly chosen according to its mature size for a site, the pruning chore is eliminated.
Reasons to Prune in a Low Maintenance Landscape
Have a reason to prune! Not all plants need to be pruned. In fact few plants need to be pruned. Formal, control-oriented gardening implements considerable pruning -- a higher maintenance regimen. Gratuitous pruning should be avoided in naturalistic, low maintenance landscapes.
- Pruning is not topping; trees and shrubs should not be topped. Topping, tipping, hat-racking or heading, is tree (plant) mutilation. Topping weakens a tree, placing them under unwarranted stress. Topped trees are more prone to breakage, sunburn, infestation by pests and pathogens. Lastly, a topped tree is an ugly, unnatural looking tree; a tree whose value had decreased to the point of being a liability rather than an valuable asset. (Why Topping Hurts Trees.)
- Prune for safety. Because we may acquire a landscape where every plant was not perfectly placed, pruning may be necessary to prevent branches or twigs from injuring people as they walk through the landscape. Trim branches to avoid having an eye poked, etc. Your landscape needn't be an obstacle course. Trim branches that intrude on walkways, doorways, paths and sitting areas unless creating a jungle environment is your objective. Rose bushes and spiny succulents (cacti, agave and yucca) may need to be relocated if they grow into common walkways and access points.
- Prune out dead, diseased and damaged wood. Dead, diseased and damaged wood is an entry point for pests and pathogens. When properly pruned, trees will compartmentalize the injury and heal themselves. The time to prune these is at the time you notice it, but it is best before the spring growth spurt.
- Prune to reduce or prevent insect problems primarily to allow for more light and air circulation. Branches that cross and rub against each other should be pruned out. This is particularly helpful with roses. Prune to the outward growing buds for a wider shrub.
- Prune to gradually rejuvenate a shrub. Over years, shrubs, especially flowering shrubs, can decline in looks and vigor. One effect of pruning is to stimulate growth. To rejuvenate, prune out the oldest and weakest looking canes and stems of a shrub down to ground level. Do not remove more than one third of the stems in any one year. Over pruning and topping reduce the number of light absorbing leaves, suddenly exposing bark and branch tissues causing sunburn which can lead to cankers, bark splitting, and death of some branches.
- Usually, when a tree or shrub has declined, dead and damaged wood has not been periodically pruned out. Do that as well. This same procedure applies to shrubs that have become tall and lanky. Remove the stem down to ground level. Be patient, and let the plant resume vigor with this staged pruning. At the same time, amend the soil. Chances are, it declined for lack of care in more than one area. In drastic cases, rejuvenation pruning may be required.
- Do not practice rejuvenation pruning on tree form shrubs.
- Rejuvenation pruning is cutting back the entire multi-stemmed twiggy type shrubs to the base when a shrub has a lot of old woody growth and few flowers, particularly hygrangeas, spiraeas, caryopteris, potentillas and sumacs. (Pruning Flowering Shrubs). This usually happens after a number of years without annual pruning to remove old growth.
- Rejuvenating or shaping of trees. It is best to hire a certified arborist to properly prune and shape landscape trees. Landscape trees are in investment and asset to your landscape. Certified arborist are educated and trained in the latest correct methods of caring for trees. (Pruning Mature Trees.) A certified arborist will require up to three years of staged pruning to properly prune a tree.
- So far, the Amarillo area has not recorded oak wilt disease. For areas with oak wilt, oak trees should only be pruned in the heat of summer and the cold of winter. Pruning cuts on oak trees should be coated with a pruning paint. (Texas Oak Wilt.) Sanitize pruning tools after cutting on oak trees.
- Prune for better shape. In a low maintenance landscape, shrubs will be chosen that don't require annual pruning for flowering. However, some shrubs benefit from early spring pruning, or cutting back. Salvia greggii, autumn or cherry sage; Caryopteris x clandonensis, blue mist spirea; Chrysothamus nauseosus, Chamisa or Rabbitbush; Anisacanthus quadrifidus, flame acanthus; and Falugia paradoxa, Apache Plume are a few of low water-use shrubs that benefit from cutting down to a third their size. I prune Salvia greggii because of its brittle wood -- heavy snow can damage the shrub. Some of my beds are amended a little too rich for low water-use shrubs; because of this, their growth is bigger than usual and they loose their compact shape. Natural pruning due to browsing by deer enables native shrubs to keep a compact shape.
- Prune for better flowering. This is done particularly on shrubs that flower on new wood. The best time to prune is after it flowers and sets any fruit. Fruitless shrubs are safe to prune right after flowering, whether they are spring, summer or fall flowering shrubs. For the others, pruning in late fall is a good time. Be careful not to prune spring flowering shrubs after the buds are present. If the shrub puts on berries, by all means do not prune, so you and the wildlife can enjoy the berries.
- Be judicious with shape-pruning. It is difficult, if not likely, to return the shrub to its natural form.
How to Prune
Proper pruning techniques are essential for the health and appearance of your plant, whether it is an herbaceous perennial, shrub or tree. Again, this does not mean that a gardener should practice indiscriminate pruning -- have a reason.
- Pruning cuts should be made just outside the branch collar. Be very careful not to cut into the branch bark collar (a ring of compressed bark at the branch crotch). Do not make cuts flush with the trunk or lateral. The International Society of Arboriculture recommends the 3 cut method. To avoid tearing the bark when removing a large heavy limb, first make an undercut 12-18 inches from the branch bark collar. Make a second cut about an inch outward and above the undercut. Now cut the stub back to the branch collar at an inward angle.
- When pruning to reduce size of the tree or shrub, take the cut back to the point of origin, or joint. On a large branch removal, cut back to a lateral that is large enough to assume the terminal role, at least one third the diameter of the cut stem. (Proper Pruning Cuts, and USDA Proper Pruning Cuts ).
- When pruning stems or canes, cut above the bud, angled slightly away from the bud, not towards it. Do not cut below the bud. The lowest part of the angled cut should still be above the bud.
- Make clean cuts, do not crush the branch or stem. Do not make any stub cuts or flush cuts.
- To avoid transmitting disease, pathogens or insect eggs, wash or sterilize the blades with each cut on trees and shrubs with these problems.
- Wound dressings such as pruning paint are not necessary after pruning. They do not aid in the healing process, and may slow it. This is except in the case of cuts on oak trees in areas affected by oak wilt.
For a healthier, natural look in pruning evergreens that overflow onto walks, paths and doorways, avoid shearing. The best time to start periodic pruning is as soon as you notice the evergreen will be or is overflowing. Use pruning shears to selectively cut out the longest overgrown branches and branch tips, leaving some branches to cover up the cut stems. Always cut back to a joint. Do not make stub cuts. Do not prune the central leader or trunk. Shearing is quick and easy, but destroys the natural shape of the evergreen. Shearing of evergreens will create a dense exterior growth that shades the interior, causing the interior foliage to die. Evergreen shrubs that have been repeatedly sheared are prone to needle browning and are subject to die back from cold winter temperatures and dry wind. You are then left with an ugly, brown, twiggy shell. Needles only grow on the growing tips out and will not grow on interior branches that are without needles. (Pruning Evergreen Shrubs).
Pruning Flowering Shrubs
Flowering shrubs are usually pruned to encourage flowering and to remove old, dead, damaged and diseased growth.
The general rule of thumb is to prune after flowering. That is, spring flowering shrubs should be pruned in early spring after flowering before spring growth when pruning out dead, damaged and diseased branches. Remove these branches from the base. Deadhead the spent flowers after spring flowering to conserve the plants energy from producing seeds and seedpods, if they are unattractive. Buds develop from midsummer through fall for the following spring's blooms. Avoid removing these twigs and branches after bud formation has begun.
Summer flowering shrubs bloom on on current year growth. Also prune summer flowering shrubs in late winter/early spring before growth begins to remove dead, damaged or diseased canes or branches. Thinning and renewal pruning should also be performed in early spring, removing the canes or branches down to the ground.
To thin a shrub that has become old and overgrown, do not remove more than one third it's branches in any one year (again, removing from the base of the shrub). Some gardeners practice annual thinning of shrubs; annually removing up to one third the branches/canes at winter's end.
Be judicious with shape-pruning. It is difficult, if not likely, to return the shrub to its natural form in later years.
Shearing does not encourage new growth at the base, nor does it increase flowering -- it is similar to blunt cutting and topping -- an unhealthy practice. Frequent shearing promotes bushiness on the exterior of the plant that shades out the interior. Overtime, you are left with an unnatural looking woody shrub with many dead branches and few flowers.
Rejuvenation pruning is cutting back the entire multi-stemmed twiggy type shrubs to the base particularly hygrangeas, spiraeas, caryopteris, potentillas, barberry (Berberis spp.), forsythia, flowering quince, honeysuckle, mockorange, flowering weigela, beautybush and sumacs. (Pruning Flowering Shrubs). Rejuvenation pruning generally will not work if more than a third of the branches are dead or without leaves. Extremely overgrown shrubs may not respond to rejuvenation pruning. Spring flowering shrubs cut back in this manner may skip a flowering year.
The upkeep, quality and selection of pruning tools is important too. Keep your pruning tools clean and sharp. To avoid transmitting disease, pathogens or insect eggs, wash or sterilize the blades with each cut on trees and shrubs with these problems. There are two basic types of pruning shears, also called clippers, snippers and secateurs: anvil and bypass pruners.
Anvil shears consist of one sharp blade opposed to a flat piece of softer metal. The sharp edge comes down as a knife on a cutting board. Anvil pruners are better for cutting out dry, hard and dead wood.
Bypass pruners work more like scissors, with two sharp blades sliding past each other. Bypass pruners make clean fresh cuts on green stems, as long as the blades are sharp. The better the quality shear, the more features it'll have, including the capability of sharpening and replacing blades. There are many styles and sizes to fit a variety of hands. These hand held shears should be used for stems or branches up to no more than 3/4 of an inch.
For stems 1/2 to 3/4 inch to 2 inches in diameter, use a lopper. Loppers have thicker blades and longer handles for better leverage in making clean cuts. Loppers come in both the anvil and bypass styles.
Pruning saws are best used for branches 1" in diameter and thicker. Pruning saws come in various sizes, many of them with curved blades.
Pole saws can reach branches up to about 14 feet and cut branches no more than a few inches thick. For pruning cuts higher up than 14 feet, consider calling a certified arborist. They are trained in safety, as well as tree care.
Dead heading is removing the spent flower to improve appearance and encourage continued flowering. Many plants are self-cleaning, that is, the spent flowers naturally drop off. Others need to be snipped at the base of the stem or pinched off just below the bud for continued blooms. Still other flowering plants will only bloom once; dead heading will not encourage additional blooming.
Plants expend a lot of energy and use greater quantities of water when producing seeds. Dead heading plants will conserve water. When you want plants to produce seeds, particularly plants that flower all summer, do not deadhead in late summer or early autumn.
Dead heading of flowers that produce prolific amounts of seed is encouraged to avoid invasive outbreaks. A little re-seeding can be good, but certain plants carry reproduction too far. Garlic chives, larkspur, the common feverfew, chocolate flower are some offenders. Naturally, all weeds should be prevented from setting seed.
While shearing of evergreens and woody perennials is not recommended, it is an effective grooming technique for herbaceous perennials. Shearing is done to promote bushiness that produces a more floriferous, compact or wider looking herbaceous plant. Shearing is mostly done on herbaceous perennials. In particular, chrysanthemums, asters, catmint, some dianthus, Engelman's daisy, blue flax (Linum perenne). I usual shear my chrysanthemums, Engelman's daisy, asters; catmint, Nepeta faassenii 'Select Blue'; and blue flax around by the second half of June and before July 4th. Ornamental grasses are sheared to within 2 to 4 inches of the ground in late winter (last week in February).
Few woody perennials should be sheared. The few woody perennials I shear are cut back to a third its size each year in early spring, such as autumn sage, caryopteris, and flame acanthus. These perennials perform similarly to herbaceous perennials in regards to shearing. Shearing is sometimes used as a quicker way to deadhead spent flowers. I have sheared Salvia greggii, autumn sage, but in years when I didn't have time to shear or deadhead it, it bloomed nicely without this maintenance.
Do Not Shear Evergreens
Do not shear juniper, yews (and other evergreens shrubs) and boxwood shrubs or hedges. Shearing hedges and shrubs is the same as topping trees. Shearing is quick and easy, but destroys the natural shape of the evergreen. The same pruning principle applies here: do not make stub cuts; always cut back to a joint. For a more healthier, natural look in pruning evergreens that overflow onto walks, paths and doorways, avoid shearing.
The best time to start periodic pruning is as soon as you notice the evergreen will be or is overflowing. Use pruning shears to selectively cut out the longest overgrown branches and branch tips, leaving some branches to cover up the cut stems. Do not prune the central leader or trunk. Shearing of evergreens will create a dense exterior growth that shades the interior, causing the interior foliage to die. Evergreen shrubs that have been repeatedly sheared are prone to needle browning and are subject to die back from cold winter temperatures and dry wind. You are then left with an ugly, brown, twiggy shell. Needles only grow on the growing tips out and will not grow on interior branches that are needleless. (Pruning Evergreen Shrubs).
Pinching back can be thought of as a form of dead heading or pruning, and is a technique performed at planting or transplanting. When pinching back a plant at planting, the plant saves energy from producing flowers until the root system is better developed. It may seem a waste to pinch or cut off blooms just after purchasing them, after all, that's why we bought them. Pinching back forces growth downward and is better for the health and development of the plant.
Some plants will produce copious amounts of blooms. For fewer, larger blooms, pinch back anywhere from a third to two thirds of the blooms, depending on the plant. This technique has been used to grow big, showy flowers, especially for flower shows or competitions.
Pinching back should be done when a plant is abnormally tall or leggy. It's always better to pinch back to a joint or down to the first set of full sized leaves. You'll be more satisfied with the look of the plant.
Advanced, Creative Grooming
In a sub-category to dead heading and pinching is creative grooming, or preemptive pruning. This does not fall within the perimeters of low maintenance, but for the low maintenance gardener with all this extra time on his hands, this activity comes under the category of want to, not have to. It's part of enhancing the garden -- advanced grooming.
Creative or preemptive pruning allows you some control in timing the blooms of some plants -- you get to mess with nature's timing a little. In a way, preemptive pruning, perhaps better known as cutting back, forces blooms -- that is, forces plants to bloom later.
Most of us gardeners have dabbled in it some, in the example of pinching back or shearing chrysanthemums through early summer. Yes, I'm one of those old fashioned gardeners who believe chrysanthemums should bloom in the fall. I don't know where we got that idea anyway, if every article about chrysanthemums mentions early pinching back. Maybe they're really a summer bloomer after all.
Pruning of roses, or delayed pruning, definitely falls into this category. I don't prune or cut back grandifloras or floribunda roses in the spring. I wait until the first bloom has finished, by late May. Technically, roses shouldn't be spring pruned until at least April 20, but who can wait that long if rose canes are long and lanky and creating quite a tangle of thorns. It's an exercise of self-flagellation to walk among the roses on a windy spring day!
In addition to the late May, first of June prune, I prune again in September and cut back the tall, bud-less canes. I have these, since shade has encroached over my rose bed, limiting re-bloom. My delayed pruning allows the heady spring flush of roses to fall on Mothers Day. And I ask you, what could be more fitting!
With a little planning and preemptive pruning or cutting back, you can time the flowering of plants for garden parties or tours. By careful and constant observation of bud formation coupled with the knowledge of flower development, you'll be able to time the blooms for a real impressive show. It is imperative to begin the cutting back early, rather than waiting until the flowers are about to open when cutting back.
The clever gardener can lengthen bloom periods of sweeps of plants by careful and judicious pruning. Stagger some of the pruning, pruning at the outer edges of swaths one week, then moving in towards the center in two weeks time. For a sweep of chrysanthemums, prune the plants on the outside shorter than those at the center, making an arch effect.
If timing is critical to a future event, it is better if you have a trial run the year before. Watch your plant, experiment, cut some back and time how long it takes to reform buds. Write down in your garden diary the date of cuts and size of buds. Don't cut all the buds, then, note the exact date in the summer the uncut buds bloom. Plants are fairly consistent year to year, given a week or two leeways. Armed with this knowledge, you'll know how long to push back bud formation. But again, this is not a low maintenance technique.
Faced with a spur of the moment visit by the garden club or friends and you've neglected your garden? -- prune and deadhead only partially into your bed and border. This works wonderfully well for wide, deep beds and borders. Most visitors only do a cursory visit of gardens and look at the front, rarely do they concentrate on the back of borders, especially if the tour is a quick walk through and not a true horticultural exploration.
A Word of Caution
As with everything else, preemptive pruning can be carried too far, especially when reading about care techniques from gentler, rainier climates. Our climate is less favorable to many of the lush foliage-rich plants people lust for, and their advice might not apply here. High plains gardeners need to become as circumspect over pruning advice befitting tropical paradises as one would on watering requirements. Investigate their gardening experience and place their advice in context.
I've admired the photographs of these time-honored gardeners and the gardens they've designed, filled with tall, showy, full-foliage perennials. These plants appear to be twice the size I've seen grow in our climate. I can understand a little preemptive pruning of Euporatorium fistulosum, and E. purpureum, Joe Pye weed, plants I thought grew too tall anyway. They can be veritable giants in humid and rainier climates.
One plant recommended by an authority on grooming is Echinacea purpurea, purple coneflower, a veritable giant in her garden. If my Echinacea purpurea ever grew taller than me, I'd consider a little preemptive pruning too. I'm lucky to see a three-foot specimen. Some years, I'm lucky to see any specimen! But, I am a little bit thrifty on the water. I do know it will grow to 4 - 5 feet, I've seen it in my mother's garden in Wisconsin, and stood in utter amazement.
Other plants recommended for pruning are some of the taller Miscanthus species, particularly Miscanthus sinensis 'Zebrinus'. I enjoy Miscanthus sinensis 'Gracillimus' and Miscanthus sinensis 'Sieberfelder' in my garden. The mature height of 'Sieberfelder" is about the same height as 'Zebrinus', about 6 1/5 feet, according to official mature growth stats by Bluestem Nursery. In my garden, a medium water-use zone, in a good year it soars to 5 feet, unplumed. During dry years, it is struggles to reach 4 feet. With preemptive pruning, we'd be left with a dwarf grass.
I do recommend reading and using other reference books. Just as gardeners should be careful with watering and soil recommendations, one should be judicial about maintenance advice from outside the region, whatever region one happens to garden in. Their gardening advice should be tempered with the knowledge of our climate and conditions.
Grooming Tips for Low Water-Use Plants
Although we may not always experience the problem of over ambitious medium and high water-use plants, our drought tolerant plants can sometimes over-reach their native stature. Planting them in over amended soil, richer than their phloem and xylem vascular tissues ever experienced in nature causes them, as well, to grow taller and floppier. When this happens, it is better for the look of the garden to cut them back. Engleman's daisy, Engelmannia pinnatifida and chocolate flower, Berlandiera lyrata, are two examples of floppy too-tall growth in composted soil.
Judith Phillips book, Plants for Natural Gardens, should be the go-to book for grooming guidance for plants more naturally suited to Panhandle gardens. Grooming information for many of the low water-use plants is still not completely known. But as gardeners acquire more and more experience, grooming tips will become common knowledge, if needed at all. For the low maintenance gardener, achieving the perfect balance between native soil and soil improvement for better garden specimens will be the ideal.