Should you deadhead your flowers?
Deadheading makes sense for repeat bloomers such as roses and highly modified annuals, such as marigolds, to keep them blooming, said Heather Stoven, a horticulturist with Oregon State University's Extension Service. For most other plants, she said, it is a matter of appearance and the personal taste of the gardener.
Plants in nature do just fine without being deadheaded, Stoven pointed out, and removing spent blossoms is rarely important for the health of the plant.
"The botanical purpose of flowers is to produce seeds so that the plant can reproduce," Stoven said. "However, when you remove flowers before they start producing seeds, the plant will still want to propagate itself, therefore it will produce new flowers to meet this goal."
No special techniques or tools are required for deadheading. Simply cut or pinch off fading blooms, being sure to remove seedpods that might have started forming behind the flower. Remove more than just the petals.
For moderately bushy plants, such as marigolds, remove each fading flower and its individual stem. Bushy plants that bloom profusely at the ends of the foliage, like coreopsis, can be sheared back with grass shears. Sometimes shearing will encourage a new flush of blooming. For plants that produce one flower at the end of a long stem, such as black-eyed Susans, cut the whole stem off at the base to avoid empty-looking stems.
Some flowers, especially annuals, can be kept blooming through the whole growing season simply by regular deadheading. Marigolds, cosmos and geraniums bloom all summer if flowers are consistently cut or pinched off as they pass their peak.
Some perennials may be deadheaded to keep them looking tidy, but it won't necessarily make them produce more flowers. The foliage of peony, Siberian iris, and lamb's ear will stay attractive through the season, but the plants won't bloom again after deadheading.
Gardeners who want to avoid "volunteers," or offspring seedlings, starting in their flowerbeds, might want to do exhaustive deadheading. On the other hand, Stoven said, it can be fun to watch your garden evolve as self-seeders like columbine or Shirley poppies come up in delightfully unexpected places.
"Cosmos and viola pop up readily the following spring with no effort on a gardener's part, if they're allowed to set seed," Stoven said. "Sometimes the seedlings produce interesting flowers, having worked with the birds and bees to do a little genetic mixing."
Before removing every spent flower in sight, be sure you know which plants produce attractive seeds or seed pods that you'll miss if you deadhead everything at the end of the summer. For instance, Gladwin iris has scarlet-orange seedpods in the fall, and some peonies also produce attractive seeds and seedpods.
"And of course, the more plants you allow to form seeds," Stoven said, "the more likely seed-eating birds will visit your garden regularly."