The Gardener Within: Master Gardener Joe Lamp'l shares tips on how to keep encourage plants to keep flowering.
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 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. Garden phlox, for example, 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.
• Single flowers. How you deadhead depends on the plant and the reason you’re cutting it back. Plants with individual flowers, like hollyhocks or balloon flowers, 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.
• Flower clusters. Clustered flowers on branched stems, like tall garden phlox, bee balm, geum and Shasta daisies, 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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• Carpeting flowers. Perennials that produce blooms over the entire plant, such as threadleaf coreopsis, baby’s breath and dianthus, 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. 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 reblooming perennials that will benefit from deadheading.
• Blanket flower (Gaillardia x grandiflora). Snip off individual flowers below the seedhead; stop deadheading in August.
• Columbine (Aquilegia spp.). Snip off spent flowers to the side stems, cut entire stem to the ground when finished flowering. Allow some seedheads to ripen if you want replacement plants next year.
• Daylily (Hemerocallis hybrids). 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.
• Jacob’s ladder (Polemonium caeruleum). Cut entire plant back to the ground to encourage new growth; let a few pods ripen to replace the short-lived parent plant. This plant often reblooms with deadheading.
• Lavender (Lavandula spp.). Harvest the flowers and the stems; cut plant back to healthy foliage to promote a second flowering. Harvest late, shorter-stemmed flowers in fall.
• Painted daisy (Tanacetum coccineum). Snip off individual flowers along the stem as they fade; cut finished stem back to basal foliage. There can be some small, sporadic reblooming.
• Purple coneflower (Echinacea purpurea). Reblooms even without deadheading; cut early blooms to a side shoot to keep later flowers large. Leave some seedheads for bird food unless reseeding is not desired.
• Stokes’ aster (Stokesia laevis). Deadhead to a side bud to prolong flowering; cut stems to the ground when finished. It may rebloom, but be careful — buds and seedheads look similar.
• Tickseed (Coreopsis grandiflora). Deadhead frequently to keep it flowering all summer; cut flower stems back to side branches. Cut all finished stems back to the ground.
Although perennials’ primary claim to fame is their reappearance in subsequent seasons, with deadheading, you can enjoy encores 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.