These general guidelines are intended to assist you in understanding why and how pruning is done. The final page (Perennials) can be taken out into the garden and will hopefully facilitate you in identifying how to prune these plants once you can identify their common characteristics. If you have questions, please call or E-mail and we will gladly assist you! Don’t be
overwhelmed… gardening is a life-long learning process…
The Principles of PRUNING:
Pruning is accomplished for many reasons. Some of these are: to direct growth, control size, remove old and diseased parts, increase flower and fruit production, enhance bark coloration, remove conflicting branches, formalize a plant’s outline, maintain plant health.
In shrubs, the most vigorous growth occurs at the terminal buds located at the ends of the
branches. When you prune terminal buds, more side shoots (lateral buds) develop making the shrub bushier. Pruning branches to the ground stimulates more growth at the base of the shrub.
During early Spring, trees and shrubs produce a hormone that stimulates cell division to develop a special protective layer of bark (similar to scar tissue). This is advantageous for the practice of pruning. Generally, the ideal time to prune is near the end of the dormant season just before growth starts in early Spring – but this is a general rule. When to prune depends on when
flowering occurs. Please read on…
When to Prune?
Spring-flowering Shrubs: These shrubs produce flower buds on wood produced the year
before. Therefore, pruning right after bloom produces the maximum amount of flower-producing wood. If you prune these shrubs during the Fall or the Winter, you will remove many flower buds for next year’s bloom!
Shrubs that sucker from the base benefit from thinning. This is the removal of interior branches with loppers or a pruning saw back to the base of the plant.
**It is good practice to remove old, heavy canes (branches) to ground level when shrubs are dormant (Winter or early Spring). Remove as much as 1/3 of the plant but not more.
Examples: Lilacs, Forsythia, many Viburnums, Honeysuckle, Chokeberry,
Mock Orange, Weigela, Flowering Quince, Redtwig & Gray Dogwood
Summer-flowering shrubs: These shrubs bloom on wood produced during the same year. Prune these shrubs when they are dormant in the Winter or early Spring before bud break. If you postpone pruning until later, you will remove flower buds for next year.
**See above notation with asterisks
Examples: Hydrangea (Annabelle and Unique), Shrub Roses, Japanese and Bumalda
Spirea, Hibiscus (Rose-of-Sharon), Potentilla, Smokebush,
Butterfly Bush, Diervilla Lonicera (Dwarf Bush-honeysuckle), Tamarix ramosissima,
Perovskia, Lonicera brownii ‘Dropmore Scarlet’, Stephanandra
Broad-leaved Evergreens: Broad-leaved evergreens require little pruning. Most grow very slowly. If pruning becomes necessary, selectively prune branches back to a side branch so that the foliage hides the pruning cuts. Broad-leaved evergreens should not be sheared or cut back into older, non-leafy areas as these plants lack latent buds. New growth is initiated from the terminal buds.
Plants that are deprived of adequate light may suffer from die-back and dead wood should be cut away. Plants that have become “drawn up” by the lack of light may be cut back hard and will soon produce new shoots.
Examples: Rhododendrons (Azaleas included here), Evergreen Hollies (Ilex)
Shrubs with Specific or no Requirements:
Cotoneaster: No regular pruning is required. Although most species will grow strongly if cut back hard, it is best to retain the natural habit. Select plants for the available space.
Dogwoods (also see ‘Spring-flowering Shrubs’): Most species need no regular pruning except for removing old and discolored canes at ground level. With Cornus mas (cornelian cherry), a decision has to be made at an early stage whether to train it as a tree or allow its tendency to branch low down. If it does make a tree, it is still desirable to retain some lower branches.
Euonymus (Burningbush): No regular pruning needed. These can be reshaped when needed by selective cutting back of the most vigorous branches to major side branches. Do not prune at ground level as this shrub grows with one trunk like a tree.
Barberry (B. thunbergii), American Cranberrybush, Koreanspice Viburnum, Diablo Ninebark: Prune in late Winter as all are deciduous. This is done to maintain desired shape and to remove dead wood; otherwise, not really necessary. Many of these are large shrubs by nature and not conducive to frequent or severe trimming.
Fothergilla, Hamamelis, Daphne burkwoodii, Hypericum, Magnolia, Rhamnus (Buckthorn), Ribes alpinum, Symphoricarpos (Snowberry), Miss Kim Lilac: No Specific Pruning Requirements Needed.
Evergreens:
Most evergreens require little pruning. These trees normally have a broad, pyramidal form with low branches with should be left intact. Never remove the central leader. Do not cut behind the living foliage of the branches into the dead zone. Once evergreens have established a dead zone, they will never grow needles in that area again.
Note: for plants that mature into large evergreen trees, pruning may never be necessary if they display nice shape and dense growth (Examples: Spruce, Pine, Fir).
Pines: Every Spring, new growth will be evidenced by “candles”. These are simply needles of the tree bound together by a sheath. As weather warms in May, you will notice the candles enlarge. To maintain a more compact, densely branched habit, remove 1/3 of these at this time before the sheath is shed. You can pinch them back with your fingers or prune them with hand pruners.
Hemlocks, Arborvitae and Yews: These have latent (dormant) buds farther back down the stem. You can shear these in late Spring or early Summer after new growth has expanded. They can also be pruned in Spring in which case pruning cuts will then be hidden by subsequent growth.
Junipers and False Cypress (Chamacecyparis): Selective pruning only if desired. Do not prune after August as the new growth will not harden off sufficiently before Winter.
General Rules and How-to of Pruning:
All plants: Immediately remove dead material. Remove rubbing, crossing and cracked branches. Remove diseased or damaged branches. Remove inward-growing branches (towards center of tree) paying particular attention to crab trees. (Examples: Crab, Purple Leaf Plum and other Prunus, Redbud)
Selectively remove branches in areas where they are tightly spaced; pay particular attention to maple trees. When branches form a narrow “V”, remove the branch closest to the center of the tree — again paying close attention to maple trees.
Deciduous trees need to be pruned to eliminate double leaders (two top stems splitting from the main trunk) and weak crotches (two top stems that have matured leaving a Y). Some trees “bleed” or exude sap from pruning wounds when pruned in early Spring. For this reason, maples, birches, elms, and black walnuts are usually pruned after they leaf out in the Spring and their sap has slowed down.
It is helpful to know that light pruning will produce even, uniform growth and hard pruning leads to the development of coarse, vigorous growth.
It is very important to know how to prune. Tools needed for pruning are long-handled lopping shears and a pruning saw. Careful, accurate pruning cuts will greatly reduce the risk of damage. When cuts are clean, plant tissue is not crushed. If buds are present, make the cut at an angle slightly away from the bud (for opposite buds, cuts should be straight across the stem). To avoid spreading disease from plant to plant, it is smart to disinfect tools. Spray Lysol or alcohol directly on your tool between prunings.
Pruning of Perennials:
Although the average perennial blooms for 3-4 weeks, many have the capacity to bloom continuously for 2-3 months if you water during dry spells, deadhead, and feed them during midsummer. By “deadheading” or removing dead flowers, seed pods are prevented from forming. This signals the plant to flower again as energy is directed back into the plant. With certain perennials, cutting back the entire plant and feeding it will encourage rebloom in the fall.
Remember that if you want to provide food for wildlife, leave seed heads and fruit on your plants throughout the Winter. Examples of these plants are Black-Eyed Susan, Purple Coneflower, Shrub Roses, and many prairie plants. This practice will also provide visual interest in the long Midwestern winter landscape.
Below are specific instructions for deadheading and maintaining perennials by category. If you observe a plant for one entire growing season, you can determine the category into which this plants falls. The categories are determined by the plant’s growing characteristics. To help you, these are indicated in parentheses at the end of each section. In time, you will become familiar with your plants and it will become second nature (pun intended!) in caring for them. Examples and instructions follow:
Spring-blooming Bulbs, Bleeding Heart (Dicentra spectabilis), Oriental Poppies: Deadhead. When foliage turns almost completely yellow, cut it back to ground level. (Plants that go dormant – no aboveground growth – during the summer)
Salvia, Shasta daisy, Yarrow, Coral Bells, Veronica, Astilbe, Bee Balm (Monarda), Liatris: A two-step process: cut off faded flowers to the next good set of leaves on the stalk; after 2-3 weeks, remove the entire stalk. Hopefully, rebloom will occur.
(Plants that have leaves all along the flower stalks with flowers at the ends of the stalks)
Daylily, Hosta, Iris, Primrose: Cut the flower stalks to the base within the crown when the last flower on the stalk has finished blooming. Don’t leave stubs.
Stella d’Oro Daylilies: regular deadheading once a week will prevent seed pod formation and stimulate the plants to produce more flowers.
(Plants that produce flowers on the ends of long, bare flower stalks)
Biennial Foxgloves, Columbine: Nothing! These are biennials that reproduce by spreading seed. If you deadhead them, you end their reproductive cycle.
(Plants that self-sow)
Foxglove (Digitalis ambigua), Phlox paniculata (the Perennial Phlox), Joe-Pye Weed, Sedum ‘Autumn Joy’, Peony: Cut faded flower heads down to a good set of leaves. Don’t leave stubs.
(Plants that bear flowers at the top of the plant and have lots of strong foliage)
Geranium sanguineum, Moonbeam Coreopsis: When blooming is almost over, use hedge clippers to shear back the plant removing ½ of the top growth. Then use hand pruners to clean up any stubs that remain. This encourages rebloom.
(Plants that tend to produce many small flowers)
Lady’s Mantle, Heartleaf brunnera: Deadhead flowers. Also once during the summer, remove 1/3 of the oldest, yellowest leaves to the base. This opens up the crown of the plant encouraging new growth.
Nepeta (Catmint), Veronica, Artemesia (Wormwood), Lamium: Cut plants back severely (by 50% or more) and feed. This forces the plant to regrow a new crown of foliage making the garden more attractive. Rebloom may also occur within 2-3 weeks.
(Perennials that have finished blooming and have old tired foliage)
Ornamental Grasses (various species): Allow grasses to stand through most of the winter. During late Winter/early Spring, cut them down with lopping shears or clippers. Reason being is simply that these grasses provide interest during our long Winters and they also provide beneficial insect shelter.
Campanula (Bellflower), Fringed Bleeding Heart (Dicentra eximia), Corydalis: Nothing! These plants are self-cleaning! When flowers are finished, they fall off by themselves so plants look great throughout the season. These plants self-sow. If you don’t want more of them, you have to weed them out – or give them away!
Purple Coneflower, Pincushion (Scabiosa), Butterfly bush: Continuously cut back the dead flowers to the next set of flower buds on the stalk. When there are no more buds, cut the stalk to its base. Feed in midsummer for continued bloom.
(Plants that bloom continuously or over a long period of time)
