A Midsummer’s Chop
A few years ago, I was gardening for a client with an overabundance of Stella d’Oro daylilies. It was August, and that season’s heat and drought had not been kind to the Stellas. Their leaves were limp, bent and yellowing. My crew and I were there to tidy up the gardens, so I made a quick decision to try a new technique: we cut the daylily leaves back to the ground. The garden looked better immediately, and by our next visit, the daylilies had resprouted with cute and tidy growth.
Many flowering perennial plants benefit from a midsummer’s trim. Here are my suggestions for what to cut and why.
Certain spring-blooming perennials will rebloom when deadheaded (removing the spent flower). Bee balm, yarrow, veronica, salvia and catmint are among the more reliable reblooming perennials. On bee balm, simply trim off the flowers as they fade, cutting the stems above a node a few inches down from the expired flowers. Yarrow and veronica flower on longer stems that are easy to differentiate from the plants’ basal leaves (leaves clumped close to the ground around the plant’s base). I usually cut the old flower stems all the way back to below the basal leaves, which promotes new flower growth and tidies the plant. Reflowering perennials will produce fewer blooms the second time around, but they’re still welcome!
Full-grown catmint and salvia plants can be cut back almost to the ground after they flower. This can be a little tricky, and it can make plants uglier until they start growing back. But I’ve found this practice effective for dealing with plants that quickly outgrow their allotted spaces and often flop over when fully grown. Within a few weeks, the plant will produce fresh new growth that will eventually flower, and you can avoid the awkwardness of trying to stake them. (New varieties of both catmint and salvia have been bred for tidier growth habits.)
REMOVING DISEASED OR UGLY FOLIAGE
By mid- to late summer, certain plant pests can be unavoidable. Powdery mildew is a plant disease that creates white or gray fungal growth on the upper sides of infected leaves. In extreme cases, the fungus quickly covers the entire plant, making fungicide treatment impossible. Peony, phlox, baptisia and bee balm, especially the older varieties, are among those perennials most susceptible to powdery mildew.
To prevent powdery mildew from spreading (and to keep my gardens from looking ugly!), I will sometimes chop diseased or damaged plants back to the ground. This works best with plants that are well established, because they’ll need a good store of energy to stay alive without continuing to photosynthesize. If you do this with peonies, know that they will not produce any new leaves during this growing season—but the plant should reappear next year. Helenium and daylilies can also survive a hard cut.
PREVENTING SEED DISPERSAL
I trim some perennials immediately after flowering to prevent their seeds from spreading around my gardens. These include liatris, rudbeckia, globe thistle, butterfly weed, echinacea and joe-pye weed. If you’re growing a wild, natural-styled garden, these plants are excellent options for reliable self-seeding. In more formal garden beds, these pollinator-friendly perennials require extra manicuring. Cut the flowers back as soon as they lose their color. If they’ve already set seeds, make sure to remove your trimmings from the gardens.
BOOSTING FALL BLOOMERS
In midsummer, fall-blooming perennials are growing vigorously, consuming as much water and sunlight as they can in preparation for their upcoming flower shows. However, upright sedums, asters and chrysanthemums can get top-heavy by bloom time. Cutting these plants back in midsummer will promote stem branching at the point of the cuts. This practice has two benefits: it helps stabilize the plant because it will not grow as tall as it normally would have and it increases flower production. Each stem that you cut will branch, giving you two flower stems instead of one. I trim these plants before July 4, which is a loose deadline to ensure the plants haven’t already started setting their flower buds. Cut each stem directly above its second or third node from the top.
Horticulturist Laura Schwarz writes and gardens in Minneapolis.