Pruning and Maintenance Tips
Regular pruning is the single best investment you can make for your landscape. When done correctly and at the right time, you enhance your landscape, improve the health of your plants, and reduce future maintenance costs. Correct pruning does not always involve shearing and, often, could be detrimental to the plant. If you have questions on any type or time of pruning, please do not hesitate to call us at 262-252-4988 and talk to one of our horticulturist. If you feel uncomfortable pruning your own landscape plants, we would be happy to send a landscape crew to assist in the maintenance of your plant and your spring and fall clean-up.
Please select the type of plant, or pruning method you are interested in learning:
TREES | SHRUBS | EVERGREENS | PERENNIALS, ORNAMENTAL GRASSES & FERNS
RENWAL PRUNING | REJUVENATIVE PRUNING | HEADING OR THINNING
THE "HAIRCUT" METHOD" | HEDGING OR SHEARING
Trees
Regular pruning is the most important thing you can do for your tree or trees. Pruning provides many benefits, but if done improperly or too much, it can be harmful. Overpruning can rob a tree of food producing leaves, delaying healing and regrowth. Learning to prune trees is not as easy as shrubs and evergreens. Pruning trees is considered an art that requires proper training and experience. We recommend calling upon a professional arborist that can give the proper care so your tree can flourish. Johnson's Nursery currently has two certified arborist that are happy to help with your tree care needs.
One type of pruning that can easily be done on ground level is Sucker Removal. Suckers are vigorous shoots arising from the roots of a tree. Most often, the suckers are from a grafted rootstock and can overtake the desired plant on top. Remove the suckers in the dormant season using a scissor-type pruning shears at or slightly below the ground line. Generally, this must be done every season, depending on the vigor of the plant.
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Shrubs
One of the most important things for shrubs is regular pruning, but without the correct pruning methods, the health of the plant could decline rapidly. There are four basic types methods for pruning shrubs: Renewal Pruning, Rejuvenative Pruning, Heading or Thinning, and the "Haircut" Method. All four methods may be used on some types of shrubs, but more often one or a few types are applicable. If you are interested in which pruning method is right for a certain type of plant, please download or Pruning and Maintenance Guide.
The best time to prune most shrubs is when they are dormant. Just prior to bud break in March or April is best, although it can be done anytime during the dormant season. When pruned at the proper time, the cuts readily seal over and new growth quickly arises. Do not prune in late summer or early fall because the new growth will not fully harden off before winter. Exceptions to the dormant season timing are early spring blooming shrubs such as Forsythia. These plants should be renewal pruned after enjoying the flowers. In our Pruning and Maintenance Guide, these plants are marked with an asterisk (*).
RENEWAL PRUNING
It is a common belief that pruning shrubs involves shearing. While this is applicable to certain types of shrubs and situations, a majority of shrubs do not respond well to shearing. Shearing can also harm the plant's natural form and become more susceptible to snow and ice damage. In most cases, renewal pruning should be used.
Most deciduous shrubs benefit from regular renewal pruning. Upon examination, you will notice that most shrubs consist of many stems or canes arising from the ground. Renewal pruning involves the selection and removal of the largest, heaviest canes at the ground line. A pruning saw or scissor-type lopper is the best tool for renewal pruning.
Renewal Pruning Benefits
-Plant's natural form maintained
-Plants height reduced
-New growth initiated below each cut, resulting in a denser plant
-Old and diseased wood removed, resulting in a vigorous, healthier plant
Over the life of the shrubs, you should only have to remove a few canes per year. The benefits of renewal pruning can be easily observed on a Redtwig Dogwood. The younger wood is more colorful, while the older, heavier canes are more woody and less colorful. Simply remove the largest diameter canes with the least color at the ground line, leaving behind the younger, more colorful stems. The following season more bright red stems will appear, giving the plant a more visual impact.
Renewal pruning is very useful on most leafy (deciduous) shrubs. Lilac, Honeysuckles and shrubby Dogwoods respond very quickly to renewal pruning. However, it does not work well for all shrubs. Burning Bush should never be renewal pruned, while other large-scale, specimen shrubs, such as Corneliancherry Dogwood and Common Witchhazel may never require it. Please consult our Pruning and Maintenance Guide for a detailed list of plants that benefit from renewal pruning.
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REJUVENATIVE PRUNING
For the bold and unafraid, many of the same benefits from Renewal Pruning can be found with Rejuvenative Pruning. While Renewal Pruning is a gradual process of thinning older wood from shrubs over a period of time, Rejuvenative Pruning is a one shot approach by removing every stem and twig just above the ground all at once.
 
Rejuvenative pruning is best done just prior to bud break in March or early April, when the plant has stored the most energy. This method works extremely well on Honeysuckle, Lilacs, and a few others. The Pruning and Maintenance Guide should be consulted as this pruning technique can kill a plant if done to the wrong plant at the wrong time.
Among the plants that benefit from annual Rejuvenative Pruning are Annabelle, Snowhill, and White Dome Hydrangea. They bloom only on new wood and, unless annually pruned back, they become floppy from the large flowers. It is important to remember that Pee Gee Hydrangea is not pruned this way and can be seriously damaged if done so. Please consult the Pruning and Maintenance Guide on pruning your Hydrangeas.
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HEADING AND THINNING CUTS
Heading and Thinning Cuts are two less dramatic types of pruning. They are useful for detail shaping or adding density to plants. Both produce slightly different results.
Heading Cuts are made just above a bud. They result in a shoot developing from the bud and often from the lower buds also. When you are making a heading cut, leave just enough of a stub to keep the bud or buds below from drying out. A slightly slanted cut is desirable where just one bud is present. However, rot may be encouraged if to large a stub is left. It may be important to prune an outward facing bud to encourage a spreading, non-congested form. The main results of Heading Cuts are an increase in density, although it can be useful in shaping.
Thinning Cuts are made just above a side branch. Make the cut just above a side branch and roughly parallel to it. Thinning cuts allow more air circulation through the plant and make branching patterns more visible. Once again, it may be more important to prune to an outward facing branch.
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"HAIRCUT" METHOD
The "Haircut" Method is a modification on the Renewal and Rejuvenative Pruning. This method is useful on both Potentilla and smaller Spireas, such as Anthony Waterer and Goldflame. In late March, spireas should be cut back to 1/3 their height, while more woody potentillas should be trimmed back to 1/2 or 2/3 their size. Next, selectively remove the oldest, heaviest twigs completely to the ground, similar to Renewal Pruning.
  
This normally involves removing 2-4 twigs per shrub. Later, these cuts will stimulate the development of new shoots and keep the plant compact, healthy, and finer textured. The "Haircut" Method should be done every 2 - 3 years to maintain plant vigor. If done every year for a number of years, the plant's stored energy reserves dramatically decrease, plus density and both flower size and quantity will decline.
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Evergreens
Pruning evergreens correctly can be a difficult task for most people. While shearing may be a viable option for many evergreens, a more natural approach may be desired.
YEWS, JUNIPERS & BOXWOOD
Generally, shrubby junipers and yews must be pruned some every year, while boxwoods require less frequent attention. Traditionally, these shrubs were sheared after their flush of growth. However, it does not have to be done this way. A more natural shape can be achieved by selecting and heading back the most vigorous branches or buds in April or early May. A second follow up may be necessary around July, particularly for yews. Not only does this maintain a more natural form, but it also creates a smaller, denser plant by inducing more lateral branching.
SPRUCE, FIR & DOUGLASFIR
Spruce, Fir, and Dougalsfir require little pruning after placement in the landscape, most pruning is done in the nursery. Any pruning done must be limited to the new growth only, since buds are not produced on older wood.
Using a hand pruners, prune back to just before existing lateral buds. This type of Heading Cut helps add density to the plant and can be useful in filling out thin areas. It is important to remember that Spruce, Fir, or Douglasfir cannot be made smaller than it already is. Also, never prune the leader. If the leader becomes broken or damaged and multiple leaders result, simply select one leader and remove the others.
PINES
Pines require a different method and are the only evergreens pruned when it is actively growing. The most commonly pruned pine is Mugo Pine and its many forms and selections. Although the principle is applicable to any type of pine, Mugo Pines must be pruned every year if keeping the plant smaller is desired.
Simply snap off a portion of the new "candle" with your fingers before it fully expands. The candle stage refers to the new terminal growth before it fully expands. Do not snap off the entire candle, since it is the only growing point of the pine. Only remove up to 2/3 of the new candle. Candle Pinching keeps the plant smaller and promotes lateral bud formation for a denser plant the following year.
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Hedging or Shearing
Hedges will always be a part of our landscape in some way, shape, or form. Generally, plants must be sheared after the new growth has flushed, but before it hardens off. Normally, this is in late May or June, although some plants may flush growth again, requiring a second, or third shearing. Remember to use sharp pruning shears so they do not tear the stems. When shearing hedges, remember three basic rules:
1. Avoid vertical sides
2. The hedge should be broader at the base than at the top
3. The top of the hedge should not be flat; rather, it should be slightly rounded to help shed snow accumulation
These rules help maximize sunlight to the sides so the hedge remains dense to the ground. In addition, this shape helps distribute snowload more evenly, avoiding damage.
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Maintenance of Perennials, Ornamental Grasses and Ferns
In the past, it was normal to cut down most perennials in autumn. This leaves the garden nearly bare or empty, a very depressing site. The inclusion of ornamental grasses, evergreens and semi-evergreen perennials in today's gardens has made our winter gardens more cheery, but it has also made seasonal maintenance more difficult.
What looks good in winter and what doesn't? Often it is the eye of the beholder. If you are unsure, leave the plants up for the winter and see if you like them. If not, cut them down the next fall. The following is a brief discussion of the five schedules for seasonal maintenance and clean up of herbaceous perennials, ornamental grasses, and ferns.
FALL CLEAN UP
The cooling nights of fall and the eventual freeze trigger plants to move their food and energy reserves to their root systems. It is after this hard freeze that it's time to cut back herbaceous plants, usually in November for Wisconsin gardeners.
Typically the above ground foliage lies on the ground after freezing or it may be dried up and withered, which holds little winter interest. Cut the dead foliage off just above the ground. If you notice plants that are not fully dormant, wait for the foliage to complete its lifecycle before cutting, as you may be hindering potential food storage for the roots.
SPRING CLEAN UP
Plants that need to be cleaned up in spring are divided into two categories: herbaceous plants with good winter interest and semi-evergreen perennials. Herbaceous perennials with winter interest include Purple Coneflower, Autumn Joy Sedum, and Siberian Iris. Their colors, structure, and seed heads make the garden more colorful and attract wildlife. After enjoying your plants for the winter, cut them back to just above the ground in early spring. This is usually in late March or early April in Wisconsin.
Ornamental grasses also add winter interest and movement in the winter landscape. If chosen to be left up in the winter, cut them back in spring. These grasses fall into two categories:
Cool Season Grass-Grasses that start their growing cycle early, usually when the soil first starts to warm in spring.
Warm Season Grass-Grasses that do not start growing until May
Cool season grasses need to be cut back in late winter to avoid shearing the new growth tips. Warm season grasses can be cut within 1-3" of the ground. A tip to ease pick up and handling is to tie taller ornamental grasses in a bundle before cutting.
Semi-evergreen perennials tend to keep their foliage color in early winter. Examples include Clara Curtis Mum, Lady's Mantle, and Biokova Geranium.
EVERGREEN PERENNIALS
Perennials in this maintenance group are green throughout the entire year. However, following an open winter, winter that lacks snow cover, their foliage often looks damaged and requires selective clean up in spring. Using a hand pruner, selectively cut off the damaged leaves to improve its looks. Examples are Bergenia, Coralbells, and Christmas Fern.
SEMI-SHRUBBY PERENNIALS
Other perennials form woody stems and tend to dieback part of the way and must be headed to increase their density and decrease their floppy nature. Examples include Russian Sage, Powis Castle Artemsia, and Tube Clematis. Follow the directions for the "Haircut" Method.
SPRING EPHEMERALS
These plants are herbaceous perennials that have similar lifecycles to tulips or daffodil bulbs. Examples of these plants include Jack-in-the-Pulpit, Virginia Bluebells, and Bleeding Heart. After they are finished blooming in the spring, these plants go dormant or dieback completely in the heat and drought of summer. At that time, they can be cut back to make a neater appearance in the landscape.
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Vocabulary
Candle - The new terminal growth on a pine before it fully expands.
Candle Pinching - A type of pruning on pines which includes removing 2/3 of the new terminal growth (candle). This keeps the plant smaller and promotes lateral bud formation for a denser plant.
Deciduous - Plants that lose all their leaves at the end of their growing season
Evergreen Perennials - Perennials that stay green throughout the year. Example: Bergenia
"Haircut" Method - A method of pruning shrubs which includes cutting back all of the stems of a shrub and completely removing some of the oldest and heaviest stems.
Heading Cuts - A method of pruning shrubs which includes cutting just above a bud, resulting in a shoot developing from the bud.
Rejuvenative Pruning - A method of pruning shrubs which includes removing every stem and twig just above the ground all at once.
Renewal Pruning - A method of pruning shrubs which includes the selection and removal of the largest, heaviest canes of a shrub at the groundline.
Semi-Shrubby Perennials - Perennials that form woody stems and tend to die back part of the way during the dormant season. Example: Russian Sage
Spring Perennials - Herbaceous perennials that go dormant or dieback completely completely in the heat or drought of summer. Example: Jack-in-the-Pulpit
Sucker - A vigorous shoot arising from the roots of a tree.
Sucker Removal - A tree pruning method which includes the removal of shoots arising from the roots of a tree at or slightly below the ground line.
Thinning Cuts - A shrub pruning method which includes making cuts just above a side branch, allowing more air circulation through the plant and making branching patterns more visable.
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