Flowering perennials look their best with a little pruning. Although pruning is a practice that is typically associated with woody plants, such as trees and shrubs, there are a variety of reasons to prune perennials. With some careful cutting, you can make some perennial plants flower more or bloom later in the season. You can also keep aggressive plants from crowding out their neighbors, reduce pests and disease, and give a plant a more attractive form.

You probably already use the most common technique for pruning perennials-deadheading. Deadheading entails removing the spent flowers from a plant. This technique improves the appearance of the plant, prevents the plant from producing seed, and sometimes encourages more bloom.

Who can resist deadheading the mushy spent flowers of iris and daylilies? If you apply gentle pressure to the spent flower near where it intersects with the stem, it will pop right off. If all the blooms on a daylily or iris stem are spent, you should cut the whole stem off near the base of the plant.

Other plants need to be deadheaded with a good, clean pair of garden shears. Use your shears to cut off the old flowers of Shasta daisies (Leucanthemum), spring asters, perennial salvias, coneflowers (Echinacea), and sun daisies (Osteospermum). If there is a stem with a flower bud that still needs to bloom coming off the main stem with the spent bloom, simply cut the main stem back to the point where it intersects with the lateral stem. If all the flowers are spent, cut the plant down leaving a nice rosette of foliage at the base.

Some spring-blooming groundcovers are best deadheaded with hedge shears. Removing the spent blooms of candytuft (Iberis sempervirens), snow-in-summer (Cerastium tomentosum), perennial dianthus, spotted deadnettle (Lamium maculatum), ajuga, basket-of-gold (Aurinia saxatilis) and creeping phlox (Phlox subulata) can be a much quicker process if you apply hedge shears or a weed trimmer to the top third or half of the plant and rake up the clippings afterwards.

Plants such as goldenrod (Solidago), perennial bachelor button (Centaurea montana), and asters, will take over your yard if you don't deadhead them. Conversely, you may choose not to deadhead coneflower (Echinacea), columbine (Aquilegia), Mexican hat (Ratibida), butterfly weed (Asclepias tuberose), and black-eyed susans (Rudbeckia). You may want these plants to seed in order to attract wildlife or produce seedlings.
Cutting back is a more radical form of pruning in which you shear a plant to about two inches above the ground.

Cutting back improves the appearance of the plant, encourages a stockier growth pattern, and stimulates new growth. Many flowering perennials need this kind of extreme haircut after they bloom. When you are cutting back some plants, such as the larger, floppier perennial geraniums, you may have to cut the plant all the way down, leaving no basal foliage. In the case of perennial geraniums, this is fine; the plant will spring right back up in a couple of days.

Pinching is a pruning technique, in which a small bit of the plant is removed before its bloom season to promote a sturdier growth habit and more compact form. The mums and asters that you buy in the fall at the nursery look so neat because growers have meticulously pinched them, and the mums in your garden can look the same. Using your fingernails or scissors, pinch off the stem just above a clump of leaves (node). You can pinch bits of the plant off gradually through the spring and early summer or you can take off one-third to one-half of the plant at once. After July 4, asters and mums should not be pinched. If you pinch later, you may prevent them from blooming before frost sets in. Goldenrod, beebalm (Monarda didyma), yarrow (Achillea) and joe-pye weed (Eupatorium maculatum) also respond well to pinching.

You can also pinch for special effects. For instance, if you are having a party or a wedding in your garden this fall, you could pinch your late summer and early fall-blooming flowers to promote a later bloom. Or if you would like to create a tiered effect near a wall, you could pinch the front part of a plant more vigorously than the back half of the plant.

Pruning is an important part of plant maintenance. You can prune to enhance the beauty of your flowers.

Plant bold colored flowers in full, bright sunlight. Pastel colors appear washed out in strong sunlight and look better in shady areas.

The signs of leaf cutter bees are showing up on roses, ash trees and other plants. The damage is easily identifiable - almost perfect semi -circular "bites" are taken out of the foliage. These bees, which look like small dark bumblebees, are important pollinators of legumes and other garden plants. The damage they do rarely affects the health of the plant, so insecticides should only be used in cases of very serious infestations.

Spittle bugs hide in the frothy, white mass of spittle commonly seen on junipers and pine
trees. The best "control " is to ignore them because they do little damage to mature plants.

Newly planted trees and shrubs will not need fertilizer until the second growing season. Adding dry, pelleted fertilizer or fertilizer "spikes" with nitrogen to the backfill soil may cause root damage.

Cicadas are the largest of the sap-sucking insects such as leafhoppers, aphids and spittlebugs. The largest cicada, the "dog-day" cicadas can be over 2" long. They develop on the roots of trees and shrubs and are usually heard and not seen. The males "sing" to attract females. Cicadas are often mistakenly called locusts which are actually a migratory grasshopper. The periodical cicadas such as the 17 and 13 year "locusts" are the longest-lived cicadas. They emerge every 17th or 13th year respectively but they are usually found east of the Mississippi River and do not occur in Colorado. Despite their large size, they cause little injury.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  June 22, 2004