Pre-emptive Pruning BY CAROLE OTTESEN HEN IT COMES to her- baceous perennials and W grasses, most people lump “grooming,” “deadheading,” and “cutting back” into the catchword “pruning,” but there are differences in each of the tasks. Pruning is a necessity in a perennial garden and almost always performed after the fact—after the winter, after the flowers have come and gone, after the growing season. Grooming removes winter-dam- aged leaves that detract from an evergreen plant’s appearance. Deadheading removes Cutting back certain herbaceous perennials and grasses at the right time will yield shapelier, more floriferous plants. spent flowers in the hopes of more to come. Cutting back eliminates tired fo- liage and restores the perennial’s neat and youthful basal clump. If you combine this kind of necessary housekeeping with a lit- tle weeding, a nutritious top dressing, and mulch, it’s the equivalent of treating your plants to a day at the spa with the works— haircut, massage, manicure, pedicure. It allows perennials to be their best selves, to stay healthy, and to contribute even more beauty to a garden. But there’s another kind of pruning that is less commonly practiced in the Garden phlox can be kept more compact by cutting them back in late spring or early summer. perennial garden, except perhaps among those who still compulsively pinch their mere maintenance and becomes a creative author of The Well-Tended Perennial old-fashioned chrysanthemums until July act. It is pruning as art, an adventure that Garden, which is a must-have manual 4. You might call it pre-emptive pruning allows certain perennials to grow into for anyone who grows perennials. Re- because it takes place before anything hap- their better-than-normal selves. Think of nowned for performing cosmetic surgery pens—before a perennial achieves its full it as the equivalent of taking your plants to on perennials, she says, “perennials are potential growth, before bloom. It isn’t a talented plastic surgeon. quite forgiving. The worst thing they’ll strictly necessary, and that is part of its That would be you. If that thought intim- do if you prune too much is not bloom appeal. Pre-emptive pruning transcends idates you, listen to Tracy DiSabato-Aust, for a year.” And they never sue! NEVELN VIVEKA 40 the American Gardener WHAT TO PRUNE tion to deadheading, she says that to Remember last summer’s Joe-Pye weed Resources keep the heavy flowering going with a (Eutrochium spp.) with those eight-foot- Herbaceous Perennial Plants (3rd few salvias, “some heavy pruning must tall flowers that required a ladder to see? edition) by Allan M. Armitage, Stipes be done yearly.” According to Clebsch, A pre-emptive height-reduction opera- Publishing, Champaign, IL, 2008. tender salvias such as Salvia microphylla, tion would have brought those flowers The Perennial Care Manual by Nancy S. greggii, and S. 5jamensis and their ma- down to eye level or below. And that kill- J. Ondra. Storey Publishing, North ny cultivars “need the protection of old er New England aster (Symphyotrichum Adams, MA, 2009. growth until there is no danger of frost. novae-angliae) that flopped and smoth- Understanding Perennials by William Then they should have heavy wood re- ered everything around it? It would have Cullina. Houghton Mifflin Harcourt moved and the whole plant should be been an ideal candidate for some well- Publishing Co., New York, NY, 2009. cut back to a reasonable size.” She cuts timed intervention. Some nips and tucks The Well-Tended Perennial Garden S. microphylla back to two inches and in midsummer would have kept it at a (expanded edition) by Tracy DiSabato- the others a little less. more manageable size and turned it into Aust. Timber Press, Portland, OR, Scott Aker, head of horticulture at the a better citizen. The same holds true for 2006. U.S. National Arboretum in Washing- many ornamental grasses, such as switch- ton, D.C., finds that cutting back certain grass (Panicum virgatum). perennials also benefits the gardener. “I While naturally tall and multi-stemmed Garden phlox (Phlox paniculata) is like to shear asters, chrysanthemums, di- plants are the most likely choices for cutting another plant that DiSabato-Aust enjoys anthuses, and rudbeckias in my home back, DiSabato-Aust has achieved showy pruning. “You can pinch early or cut it garden so that I don’t need to spend a lot results with smaller, more compact plants back by one half. Or cut it back by four to of time staking them later,” he says. such as balloon flower (Platycodon grandi- six inches when it’s in bud. It’s a really fun Not all perennials can be pre-emptively florus) and Autumn Joy sedum (Hylotele- plant to experiment on.” pruned, however. For example, crocos- phium ‘Herbstfreude’). The latter is not Salvias might also seem to be un - mias, torch lilies (Kniphofia spp.), and typically cut back because it has a naturally expected candidates for pre-emptive astilbes don’t take kindly to it. Neverthe- neat, uniform habit. However, pruning this pruning, yet California gardener Bet- less, most others come out from under the sedum produces a remarkable effect. After sy Clebsch, author of The New Book of knife with better form, a later and, possi- pre-emptive pruning, it seems to flow over Salvias, practices what she calls “creative bly, longer bloom period, and a shorter, the ground like a tide of copper flowers. pruning” on certain species. In addi- more compact habit. Many tall herbaceous perennials that flower in late summer and early fall, such as the New England aster (Symphyotrichum novae- angliae) shown here, can be cut back in early to midsummer, when they are about two feet tall, above. By fall, the pruned plants, right, have grown back shorter, with a more sculpted appearance and abundant purple flowers. CAROLE OTTESEN(2) VIVEKA NEVELN VIVEKA March / April 2014 41 Pre-emptive pruning does much more TRY YOUR PRUNERS ON THESE PLANTS than simply limit size. Perennials such as The following mid- to late-summer bloomers shape up well after being cut back: asters can be sculpted into elegant mounds of flowers by cutting the plants shorter Botanical name Common name around the edges and leaving the center a Artemisia ludoviciana white sage little taller. Or, for a mass of perennials that Aster tataricus Tartarian aster all bloom facing in one direction, cutting Asteromoea mongolica Mongolian aster those in front very short and graduating the (also listed as Kalimeris mongolica) plants’ heights as you move back will result Boltonia spp. boltonia in a slope of flowers with all plants in view. Dendranthemum 5grandiflora hardy garden chrysanthemum To manipulate bloom time, you can Echinacea purpurea purple coneflower cut back portions of a planting to stag- Eutrochium fistulosum Joe-Pye weed ger and lengthen overall bloom times by Eutrochium maculatum spotted Joe-Pye weed Helianthus spp. perennial sunflower Miscanthus sinensis miscanthus Monarda spp. beebalm Phlox maculata wild sweet William Phlox paniculata garden phlox Rudbeckia nitida shiny coneflower Solidago spp. goldenrod Symphyotrichum novae-angliae New England aster Symphyotrichum novi-belgii New York aster Tricyrtis spp. toad lily Autumn Joy sedum, which is generally a tidy plant even without pruning, becomes extraordinarily compact with it. weeks. Just be careful not to overdo the delaying tactic or you risk losing a year’s ‘Lemon‘Lemon Queen’Queen’ perennialperennial sunflowersunflower ‘Lightning‘Lightning Strike’Strike’ toadtoad lilylily worth of flowers. However, “don’t be afraid to exper- iment,” advises Aker. “You’ll find what works through trial and error.” So as you head out to neaten up the WHEN TO PRUNE in growth and bloom time, DiSabato-Aust garden this spring and summer, think Knowing when to prune plants is crucial gauges the time to cut back late summer- beyond your usual maintenance chores. for the best results. “In general, plants in and fall-blooming perennials by size rath- You can use your pruners like a scalpel your region that normally bloom after er than by date. “When a plant reaches to enhance your plants’ natural beauty. the summer solstice are the ones that can roughly 16 to 24 inches,” she says, “it can And as you snip, chant the mantra “less be pruned until early July,” says Aker. be cut back. Normally it’s cut back by half, is more, lessismore, lessizmore.” m “Don’t cut back plants like peonies, that but sometimes it can be two-thirds of the flower in early summer, because they will plant.” The more vigorous the plant, the Carole Ottesen is a contributing writer for have already formed flower buds.” more can be trimmed away. In her experi- The American Gardener. This is an updated Because climate, location, and weather ence, the foliage will usually regrow within version of an article originally published in conditions make for enormous differences 10 to 14 days, depending upon the weather. the March/April 2004 issue of this magazine. RIGHT:LEFT TO COURTESYOF BAILEYNURSERIES; COURTESY OF TERRANOVANURSERIES;CAROLE OTTESEN 42 the American Gardener.