The Gardener Within: Tips on how to keep a perennial flower garden looking its best from master gardener and author Joe Lamp'l.
There’s nothing more rewarding to a gardener than watching a garden come to life after a long winter. But as the summer progresses, many of those wonderful blooming plants start to look a little worse for the wear. A lot of that worn look comes from spent flowers going to seed. The cure is deadheading.
Besides cleaning up a ratty appearance, deadheading keeps some perennials from reseeding all over the place. For example, garden phlox (Phlox paniculata hybrids) doesn’t breed true, so the seeds from the cultivar you planted will look different from its parent plant, and could crowd it out altogether. By removing spent blossoms before they set seed, you can also prolong bloom time or even stimulate a second blooming in some perennials. Preventing seeds from ripening also keeps the plant stronger and healthier.
How you deadhead depends on the plant and the reason you’re cutting it back. Plants with individual flowers, like hollyhocks (Malva sylvestris), Zones 4-8, or balloon flowers (Platycodon grandiflorus), Zones 3-8, bloom for weeks. But the older flowers wither as new ones open, leaving exhausted blossoms along the stem. Snip off each pod as it fades. The plant will bloom longer and the later flowers will be nearly as large as the early ones. After the stems are finished, cut them to a low mound of foliage or all the way to the ground.
Clustered flowers on branched stems, like bee balm (Monarda didyma), Zones 4-9, and Shasta daisies (Leucanthemum x superbum), Zones 5-9, need a little more snipping to keep them blooming and to prevent reseeding. Seeds can ripen early and drop before the whole cluster turns brown, so as soon as the main panicle withers, cut it back to a side shoot. These side shoots will then start to mature and prolong the plant’s flowering time.
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Perennials that produce blooms over the entire plant, such as threadleaf coreopsis (Coreopsis rosea), Zones 4-8, and garden phlox (Phlox paniculata), Zones 4-8, need to be sheared. As soon as the majority of flowers fade, snip them off so you won’t be looking at blankets of brown all summer. If there is a good-looking mound or rosette of foliage under the flowers, leave it and remove only the spent flowers with scissors or sharp bypass pruners. Hedge shears will do fine if you’re cutting all the way back to the ground. The plant will be back with a neat mound of foliage, and maybe even some late-season flowers, in a few weeks.
Here are a few more reblooming perennials that will benefit from deadheading.
Purple coneflower (Echinacea purpurea). Full sun; Zones 3-9. A reliable rebloomer, even without deadheading; cut early blooms to a side shoot to keep later flowers large. Leave some seed heads for bird food unless reseeding is not desired.
Blanket flower (Gaillardia x grandiflora). Full sun; Zones 3-11. Snip off individual flowers below the seed head; stop deadheading in August.
Perennial geranium (Geranium spp.). Full sun; Zones 5-9. Gently pull spent flowers and their long stems by hand without uprooting the main plant.
Daylily (Hemerocallis hybrids). Full sun; Zones 3-9. Snap off wilted flowers to keep later blooms as large as possible; once a stem is finished, cut it to the ground. Not all cultivars rebloom.
Bleeding heart (Dicentra spectabilis). Part sun to shade; Zones 3-9. Cut spent flowers and stems off at base of plant.
Salvia “May Night” (Salvia x sylverstris “May Night”). Full to part sun; Zones 5-9. Trim the dense, indigo blue spikes and stems at the base of the plant.
Painted daisy (Tanacetum coccineum). Full sun; Zones 4-9. Snip off individual flowers along the stem as they fade; cut finished stem back to basal foliage. There can be some sporadic reblooming.
Perennials return season after season, but with deadheading, you can also encourage many to make an encore flowering later in the same season.
Joe Lamp’l, host of “Growing a Greener World” on PBS, is a master gardener and author. For more information visit www.joegardener.com.
Some plant may be considered noxious weeds in your area. If you’re not sure what plants may be invasive in your area, check with your local garden center, horticultural office or noxious weed control board.