A few simple pruning techniques can make your perennial garden the envy of your neighbors all summer long.
Beginning gardeners quickly learn after planting even a small perennial bed that there is maintenance involved. Even daylilies, one of the easiest perennials to grow, require some attention to look their best in your garden. Lest you worry that the following suggestions will burden you with an even longer to-do list, try to think of maintenance in the perennial garden as simply gardening.
Deadheading, the process of removing dead blooms from a plant, is done for several reasons:
To encourage the plant to produce more blooms
To improve the general appearance of the plant
To prevent self-seeding (unless that is desired for a particular plant)
Most deadheading can be accomplished with bypass pruners or pruning scissors. The most common method is to cut the spent flower and stem down to the next lateral bud (see Image A below), flower head, or leaf. Some examples of plants that are deadheaded in this manner include Echinacea purpurea (coneflowers) Phlox paniculata (garden phlox), Salvia, and Monarda didyma (bee balm). The black horizontal lines in the diagram below show where to make the pruning or deadheading cuts for three different kinds of plant forms. Note that A and C are cut down to the next set of lateral leaves, but B removes the entire flower stalk at the base since no additional flowers will be produced on this stem.
Plants that flower repeatedly along the same stems like Platycodon grandiflorus (balloon flower) and Campanula persicifolia (peachleaf bellflower) can be deadheaded by using your thumb and index finger to pinch off individual spent blooms. This can extend the blooming window significantly. Don’t cut the stems down until the end of all flowering or you will lose the opportunity for new blooms.
The spent blooms on Hemerocallis (daylilies) also require no tools other than your fingers. Simply snap the mushy flowers off with your fingers, taking care not to accidentally remove buds waiting to open. This will not increase the number of blooms on your daylily, but the overall appearance of the plant is much more attractive and photo-worthy. When all the buds have opened, cut the stems down to the ground with your pruners.
Heuchera (coral bells) and Hosta are examples of plants whose flowering stems should be cut to the ground after flowering has finished. The same can be done with Alchemilla mollis (lady’s mantle). If your lady’s mantle seems to be taking over your garden, you can pull up the stems with your hands along with some of the roots which will thin the plants at the same time.
Cutting back or shearing is the removal of foliage, including leaves and stems. This task can be done with bypass pruners or more comfortably with hedge shears. Taking off a significant amount of foliage can be unsettling if you are doing it for the first time, but the plant will recover even more quickly than your own head of hair after a bad haircut! Cutting back plants has several benefits:
Improving plant appearance after spring or summer flowering has finished
Controlling the height of a plant before flowering and reducing the need for staking
Reducing the incidence of diseases or pests by removing dead or dying leaves
Many spring-blooming plants such as Phlox subulata (moss phlox) and Dianthus deltoides (maiden pink) look less ratty after blooming when sheared by about half. In fact, many low-growing plants of this nature can be pruned this way. A taller spring-bloomer, Euphorbia epithymoides (cushion spurge), can be cut back by a third of its height and shaped after blooming to control the plant’s tendency to fall open in the center later in the summer.
Summer-blooming perennials like Geranium sanguineum (bloody cranesbill) can be cut down to the new basal foliage (new leaves and stems at the base of the plant) that are already growing under the tired and sprawling foliage in late summer. Reblooming is less dramatic, but the fresh new foliage is more appealing and turns red in the fall. Salvia is another summer-bloomer whose foliage can look tired after blooming has concluded. When deadheading is no longer giving you new blooms, cut the entire plant down to the new basal foliage. You will be looking at a fresh new plant that may even rebloom sporadically. Likewise, Echinops ritro (globe thistle) can be cut down to new basal foliage in late summer and new flowering will occur but not profusely. The plant will not rise to the same height, however, so if you want something tall to remain in that space, leave it standing for the finches to enjoy the seedheads.
One solution for floppy summer and fall-blooming perennials is to cut them back before flowering to control the overall height of the plant and reduce the need for staking. Symphyotrichum novae-angliae (New England aster) can be cut back in early to mid-June by half to two thirds. Plants will still reach 3 feet in height, and flowering is not reduced. Likewise, Sedum telephium such as ‘Autumn Joy’ can be cut back in early June to about four inches to reduce the tendency of the plants to fall open in the center, much like Euphorbia will do. Blooms are not reduced by this practice, and plants have a more pleasing form.
Finally, removing leaves but not stems, known as deadleafing, may be necessary to control the spread of insects and diseases and improve a plant’s appearance. Dead or dying leaves may indicate a problem with light or moisture, but sometimes it’s just part of the plant’s life cycle. Because dead and dying leaves may harbor insects or diseases, it’s best to pinch or cut them off. Some insects like the fourlined plant bug can make individual leaves on some perennials look rough by the time these sucking insects have finished feeding in early July, but they generally do not harm the plants, and usually the plant’s appearance can be greatly improved by simply pinching off the leaves they have been feeding on.
Tending to your plants need not be an unpleasant chore. Strolling through your garden with your pruners can be great nature therapy. Think of it as a bonding experience with your plants! And don’t forget to have your camera handy for those moments that take your breath away.
The third edition (2017) of The Well-Tended Perennial Garden by Tracy DiSabato-Aust is a comprehensive text on planting and pruning techniques published by Timber Press that also contains a helpful encyclopedia of perennials with specific pruning techniques for each plant. This is an extremely valuable resource for dedicated deadheaders!
For a short list of spring-blooming perennials that can be cut back after flowering, see “Pruning Perennials for Better Shape,” University of Illinois Urbana-Champaign Extension at https://aces.illinois.edu/news/pruning-perennials-better-shape
iStock photo by Lex20
Title: “How to deadhead different plant growth forms”
Creator: Renee Lampila
Title: “Deadheading daylilies”
Laurel Watt grows a wide range of perennials on her small lot in the Macalester Groveland neighborhood of St. Paul. She joined the Ramsey County Master Gardener Volunteer Program in 2020.