Deadheading: When, how and why

URBANA, Ill.  - As with any profession, there are terms known and understood only by the “professionals,” said a University of Illinois Extension horticulture educator.

“Auto mechanics and computer technicians seem to speak their own language,” said Martha Smith. “I came to realize so do gardeners, as was pointed out by a friend when I nonchalantly said her flowers should be ‘deadheaded.’ This is beyond the Latin thing, which many feel is just a horticulturist showing off, but actually is to clarify exactly what is being discussed. There are terms such as pinching, disbudding, stippling, and deadleafing that really can be confusing.”

Deadheading is removing old flowers. It also can involve removing foliage to improve the appearance of the plant. “Consider the lovely tall bearded iris. This perennial can have two to four blooms along its stem in May. As they finish flowering, they go from stunning to mush-on-a-stem.

“Hand pick each flower as it finishes to improve the appearance. Once all have bloomed, cut the stem back to the basal foliage,” she said.

The popular daylily (Hemerocallis sp.) is another flower that looks so much better deadheaded. Daylilies can have four to eight buds in a cluster at the end of a flower scape (another word that many may not be familiar with – flower stalk). As the name suggests, each flower blooms for a day.

“It would be so polite of this plant if the old flowers simply dropped off but, no, we need to deadhead and individually remove the old flowers,” Smith explained. “Once they have all bloomed out you cut out the flower scape. Don’t forget annual plants, as well. Remove old geranium, marigold, and gazania flowers and you will again have a full blooming plant.”

There are other plants that bloom in a flurry with many flowers covering the plant. Threadleaf coreopsis is an example. Sunny yellow flowers cover the plant for three to five weeks starting in June. Once they are bloomed out, simply lop off the flowers with sheers, plus about 3 to 5 inches of growth (depending on cultivar). This may seem a bit bold but the plant will respond with a flush of new crisp foliage and usually a second flush of flowering – though not as prolific as the first flush, Smith said.

Other plants such as Speedwell (Veronica sp.), perennial Salvia, or Spiderwort (Tradescantia sp.) often look haggard after they bloom as the heat of summer kicks in. ‘Silver Mound’ Artemesia often breaks open and looks so sad. Clean up these plants simply by deadheading after bloom but also removing most of the foliage. Cutting back to basal growth to 4 to 5 inches may leave an open spot in your garden temporarily, but these plants will respond and reward you with compact clean growth.

“Another advantage to removing old flowers and foliage is preventing seed production,” she said.  “Not only does this take energy from overall plant growth, but with some plants this can be a source of re-seeding. Purple coneflower (Echinacea sp.) is known to reseed. Deadhead and you eliminate this issue. But, if you want to attract birds to your garden, then let the flowers remain and don’t complain when you have little coneflowers throughout the garden.

Source: ACES