Let’s face it – there’s always something to do in the perennial garden. Besides the usual soil preparation, planting, weeding, watering, fertilizing, etc., there’s lots of grooming to be done. By grooming, I mean keeping perennials looking lush, healthy, and colorful starting in spring and ending with the first killing frost in fall. Here are nine easy-to-master grooming methods for keeping your perennials looking their best.
DEADHEADING SPENT BLOSSOMS
Deadheading is the practice of removing old or spent blossoms just after they fade. This grooming technique:
- Improves the overall appearance of the plant.
- Extends the period of bloom by diverting the plant’s energy into pushing out new flowers instead of setting seed.
- Encourages a second flush of blooms later in the season on some but not all perennial species. Sea thrift (Armeria), peony (Paeonia), and leopard plant (Ligularia dentata) are examples of perennials that are genetically programmed to bloom only once per season. Deadheading will not encourage them to re-bloom.
- Prevents self-seeding of plants that you may not want to spread, such as clustered bellflower (Campanula glomerata) or rose campion (Lychnis coronaria).
- Keeps the foliage looking attractive much longer. By preventing seed production, the plant diverts its energy to the foliage, keeping it attractive for a longer period of time.
While these are some of the benefits of deadheading your perennials, there’s no rule that says you must deadhead them. In fact, some gardeners prefer to leave their gardens in a “wild” or more natural state, which reduces the amount of maintenance required. Other reasons for not deadheading include:
- Self-seeding. Letting some species such as columbine (Aquilegia), woodland phlox (Phlox divaricata), or orange coneflower (Rudbeckia fulgida) self-seed naturally is a great way to acquire lots of new plants for free. Keep in mind that plants grown from the seeds of hybrids will not resemble the parent plant.
- Habitat for wildlife. Leaving plant stalks and seedheads in place over the winter provides food and habitat for birds, overwintering insects, and other wildlife creatures.
- Winter garden interest. The seedheads of some perennials such as Joe Pye Weed (Eutrochium), tall sedum (Hylotelephium), coneflower (Echinacea), false indigo (Baptisia australis), and grasses provide plenty of visual interest in the winter garden.
Deadheading is easy to do but, for best results, remove both the spent blossom and the stem just below the blossom. To do this, follow the spent flower stem down to approximately 1/4 inch above a new lateral flower, flower bud, or leaf pair. Snip the flower stem off at that point using clean, sharpened hand pruners or scissors.
Examples of perennials that respond well to deadheading include:
- Black eyed Susan (Rudbeckia)
- Blanket flower (Gaillardia)
- Butterfly weed (Asclepias tuberosa)
- Culver’s root (Veronicastrum virginicum)
- Garden phlox (Phlox paniculata)
- Large flower tickseed (Coreopsis grandiflora)
- Perennial sunflower (Heliopsis helianthoides)
- Purple coneflower (Echinacea purpurea)
- Shasta daisy (Leucanthemum)
- Stokes’s aster (Stokesia)
CUTTING BACK FLOWER STALKS
This technique is a more drastic form of deadheading and is generally used on plants with flower stalks that have finished blooming or look withered, yellowed or brown, or otherwise look unappealing in the landscape. After all the blooms have faded on the flower stalk, cut the entire stalk all the way down to the basal foliage (growth just above the soil level) using hand pruners. This practice:
- Stimulates new growth and possibly a new round of flowers, depending on the species.
- Helps control disease or insect damage.
- Improves the overall appearance of the plant.
- Extends the life of some plant species.
In addition to the perennials listed under the heading of deadheading above, the following will also respond well to having the flower stalks cut back to basal growth:
- Beardtongue (Penstemon)
- Daylily (Hemerocallis)
- Gayfeather (Liatris)
- Goldenrod (Solidago)
- Hosta species
- Lance-leaf tickseed (Coreopsis Lanceolata)
- Lungwort (Pulmonaria)
- Salvia
- Speedwell (Veronica species)
- Yarrow (Achillea millefolium)
CUTTING ENTIRE PLANT BACK
This grooming method can be done on some declining perennials to encourage vigorous new growth and possibly even extend the life of the plant. Spring blooming perennials such as columbines (Aquilegia) and lungwort (Pulmonaria) or summer-blooming perennials such as spiderwort (Tradescantia), daylilies (Hemerocallis), and tickseed (Coreopsis lanceolata, which can bloom itself to exhaustion) can be revitalized by either cutting the foliage back to basal growth or cutting it all the way to the ground. Since this is a somewhat drastic grooming technique, it’s wise to research the plant first before cutting it back. Also, it’s best to avoid this technique if the plant is enduring an extended drought or other stressful growing condition.
SHEARING
Another form of deadheading, shearing removes some of the top growth of a plant in addition to the spent blossoms. This technique is ideal for perennials with lots of tiny flowers that bloom all at once. For these perennials, it’s more efficient – and less frustrating – to shear the entire plant rather than deadhead each individual spent flower. You may remove some unopened buds using this technique, but that’s a small price to pay for a fresh new round of blossoms a couple of weeks later. Use garden shears rather than hand pruners to remove about a third to one half of the top growth and spent flowers. For best results, follow the natural shape of the plant as you shear.
Perennials that benefit from being sheared include:
- Candytuft (Iberis sempervirens)
- Catmint (Nepeta)
- Tickseed (Coreopsis verticillata)
- Hardy Geranium species
- Lavender (Lavendula species) – Shear back to just above the woody stems.
- Pinks (Dianthus species)
- Russian Sage (Perovskia)
PINCHING
If you’re confused about deadheading versus pinching plants, here’s the difference between the two techniques: Deadheading removes blossoms that are faded or spent whereas pinching removes the growing tip (terminal bud) of a stem or branch and the first set of leaves. This latter technique stimulates more lateral growth, which increases the number of flowers. In addition to creating a bushier, more compact plant, pinching delays the bloom time by 2 to 3 weeks. For example, some chrysanthemums (Dendranthema) start showing color in August. But if you want them to bloom later, pinch the stem tips back once or twice in late spring or early summer but no later than early July. Otherwise, the plant may not be able to push out new buds in time to bloom before the first killing frost kills them. If the stem tissue is soft enough, use your fingers to pinch off the tip growth or snip it using clean, sharp hand pruners.
Perennials that benefit from pinching include:
- Beebalm (Monarda)
- Chrysanthemum (Dendranthema)
- Garden Phlox (Phlox paniculata)
- Goldenrod (Solidago)
- Joe Pye Weed (Eutrochium maculatum)
- Purple coneflower (Echinacea purpurea)
- Shasta Daisy (Leucanthemum)
- Sneezeweed (Helenium autumnale)
- Turtlehead (Chelone glabra)
- Yarrow (Achillea)
DEAD-LEAFING
Dead-leafing is a term author Tracy DiSabato-Aust uses in her book The Well-Tended Perennial Garden. It simply refers to pinching or snipping off leaves that are dead or damaged due to sun scorch, lack of water, disease, insect and animal chewing, or weather. It also refers to cleaning up dead foliage from spring-flowering bulbs such as daffodils or tulips.
DISBUDDING
Disbudding is not so much a grooming technique as it is the practice of limiting the number of buds on a plant. It allows the plant’s energy to go into inducing the terminal bud to grow larger. When side buds are about the size of a pea, pinch them off plus any side branches, leaving only the terminal bud in place. This results in one larger than normal flower on a long stem. In some cases, the larger flower may also be heavier, requiring staking to keep it from falling over.
Although disbudding is commonly used by gardeners who compete in judged flower shows, the technique can be used by anyone regardless of gardening skill level. For the home gardener who wants to experiment with disbudding, some candidate perennials include dahlias, peonies (Peonia), carnations (Dianthus), and chrysanthemums (Dendranthema).
THINNING TO REDUCE CROWDING
This is the practice of removing selected stems from plants that may have grown too large or too crowded. Thinning helps to increase air circulation, increase light levels, prevent plant diseases such as powdery mildew, encourage better branching on interior stems, and produce a sturdier plant. The goal is to prune out a third of the stems (preferably the weaker or thinner stems) at ground level in the spring when the plant is about a quarter to a third of its mature size. Thinning may result in fewer flowers, but the plant will be able to direct its energy to the remaining flower stalks, resulting in larger flowers on some perennial species. Thinning some perennials such as garden phlox (phlox paniculata), bee balm (Monarda), and aster species helps reduce the risk of fungal diseases such as mildew or rot.
PRUNING USING THE “CHELSEA CHOP” METHOD
Loosely defined, the “Chelsea Chop” is a pruning method used to selectively cut back or pinch back certain perennial species that bloom in mid- to late summer or fall. The timing of this method generally coincides with the Royal Horticultural Society’s Chelsea flower show in the latter part of May, hence the name. This is approximately the time of year when the plants have achieved most of their vegetative growth and can endure the method without significant damage to the plant’s health.
The Chelsea chop is done for a variety of reasons, including the following:
Delay Bloom Time: Use hand pruners or shears to cut back a plant by one-third to one-half. This method delays blossoms until later in the season and keeps the plant shorter and more compact. The plant may look bad for a few days, but it will quickly leaf back out again and will be none the worse for wear.
Extend Bloom Time: Randomly select about half of the stems throughout the plant and only cut those back by one third to one half. The uncut stems will flower first, followed by the pruned stems, thus prolonging the overall bloom time.
Stagger Floral Display: Cut the stems at the front edge of the plant by one third to one half but leave the back half alone. This will create a tiered effect with the back half of the plant blooming first followed later by the blossoms on the front half.
Perennial species that benefit from being cut back one third to one half of their vegetative growth in late spring or early summer are ones that typically bloom later in the season – midsummer through fall. A few examples include the following:
- Aster (Symphyotrichum)
- Bee balm (Monarda)
- Chrysanthemum (Dendranthema)
- Garden Phlox (Phlox paniculata)
- Goldenrod (Solidago)
- Cardinal Flower (Lobelia cardinalis)
- Perennial sunflowers (Helianthus)
- Purple coneflower (Echinacea)
- Sneezeweed (Helenium)
- Tall Sedum (Hylotelephium)
This method should not be used on species such as peonies or irises, which bloom in late spring and are done for the rest of the season. Deadheading (removal of spent blossoms) is all that is needed to tidy up the plants. This method also should not be used on woody sub-shrubs, such as lavender.
SUMMARY
Pruning perennial species using the methods described above can take an ornamental garden from ordinary to extraordinary. It takes a practiced eye to know which pruning technique to use on a plant and when — but, in general, the plant can guide you as you observe its habit and texture. If in doubt, experiment first on one or two stems before committing to any of these techniques. Observe the results before deciding which approach will work best.
For more information on general care and maintenance of the ornamental garden, be sure to check out the tasks and tips In the Ornamental Garden which appears monthly in The Garden Shed newsletter.
FEATURE PHOTO CREDIT: Pat Chadwick
SOURCES
The Perennial Care Manual: A Plant-by-Plant Guide: What to do & when to do it (Ondra, Nancy J., 2009)
The Well-Tended Perennial Garden – An essential guide to planting and pruning techniques, Third Edition, (DiSabato-Aust, Tracy, 2017)
The Know Maintenance Perennial Garden (Diblik, Roy, 2014)
Care for Perennial Gardens with 3 proven pruning methods, University of Illinois Urbana-Champaign Extension
Pruning Herbaceous Plants, Pennsylvania State University Extension
