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What you need to know about deadheading

by Timber Press on March 16, 2017

in Gardening

‘Alpha’ phlox being deadheaded to a lateral bud to extend the bloom period. Photos by the author and illustrations by Beth Ann Daye.

As the “deadhead queen,” I frequently speak and write on the importance of removing old or spent dead flowers. If you are looking for more information about rock ’n’ rollers, this is not the right place, although that might sound somewhat more intriguing. . .


Deadheading is beneficial to most herbaceous ornamental plants. Usually there is deadheading to be done from spring to killing frost. You’ll enjoy the process more and are less likely to feel overwhelmed if you keep up with it. There are many reasons for deadheading. Primarily, deadheading can prolong the bloom period for plants on which the flowers open over a period of several weeks, or it can initiate a second flush of smaller, sometimes shorter and less numerous blooms on plants that have a single heavy bloom. It can improve the overall appearance of the plant, giving a fresh new look to an otherwise finished or even distracting item. It can persuade biennials to behave like perennials. It can prevent self-seeding. I also like to remove deadheads or seedheads that weigh down the plant’s foliage. Seed production can drain a plant’s energy, and consequently, with certain perennials it can cause the foliage to deteriorate.

Deadheading can promote vegetative and root growth rather than seed production and help retain the plant’s healthy appearance. The age of a plant greatly influences its deadheading needs. New plants give the gardener a grace period by requiring less frequent deadheading in their first year in the garden. The honeymoon, so to speak, is over after that first year, however, as deadheading hits full force the second season. Weather also greatly affects deadheading from season to season, with cool, moist weather extending the bloom life and sweltering heat and pelting rain decreasing it.

Basic botany for the perennial plant pruner, here showing the basic structures of Shasta daisy (Leucanthemum ×superbum).

How to deadhead depends on the particular growth habit of the plant. The most common question I hear from people is how far down they should prune. Sometimes you need to remove individual dead flowers one at a time, or remove whole clusters of dead flowers, or cut off the entire flowering stalk. Because deadheading, like other forms of pruning, is so species-specific, it is difficult to categorize or group plants into neat compartments. A key thing to look for when deadheading is the presence of new buds or new flowers. If they are present, deadhead to the new buds or flowers.

Questions often arise about when to deadhead a plant that has a flower spike on which the flowers at the bottom of the spike open first, in which case the flowers at the bottom start to develop into seed while the flowers near the tip of the spike are still opening. (This flowering pattern is technically termed indeterminate.) If let go too long, such a plant will often produce rather long and gangly looking flower spikes, full of seed capsules and with 2 or so little flowers overwhelmed at the tip. This may be a personal preference, but it is best not to let things go this long. A rule of thumb would be to deadhead when the seedpods outnumber the flowers or when the spike is about 70 percent finished with flowering.

Deadheading for perennials with foliage on the flower stem, here showing Heliopsis helianthoides.

The majority of perennials require deadheading to a lateral flower, bud, or leaf. Plants of this type include popular perennials like Shasta daisies, yarrow, salvia, and veronica. After all flowering is finished, many of these perennials also require further cutting down to basal foliage. To deadhead, prune off the dead flower stem to a new lateral flower or, if visible, to a lateral bud; if neither are apparent, cut the old flower off at the first lateral leaf. Many perennials can also be deadheaded by shearing, thus eliminating the tedious task of deadheading each individual old flower above a lateral leaf.

Plants like balloon flower (Platycodon grandiflorus) and peachleaf bellflower (Campanula persicifolia) require careful deadheading of each individual flower along the stem. New buds are produced adjacent to the old flowers along the stem, and if the stem is cut back to the foliage before this flowering is completed, the bloom period will be greatly shortened. Perennials such as Gypsophila paniculata, Scabiosa columbaria ‘Butterfly Blue,’ and species of Aquilegia and Hemerocallis, which have branching flowering stems, also require careful attention to detail when being deadheaded.

The ugly deadheads or “mush-mummies” of daylilies are not attractive additions to any garden and are best pruned off .

Deadheading for these plants involves cutting the old flower and its stem down to a lateral flowering stem or bud; then, when this next lateral stem or bud is done flowering, it is cut down to another lateral flowering stem, if present, or, if not, to the basal foliage. With daylilies (species of Hemerocallis), the individual deadheads— which become wet, slimy, mummy-shaped dead flowers or, as I like to call them, “mush-mummies”—first should be pruned or snapped off using your fingers, taking care not to damage any of the new buds. When no more new buds are visible in the bud cluster, the entire flowering stem should be cut off at the base.

 

Tracy DiSabato-Aust has earned international acclaim as one of America’s most entertaining and knowledgeable garden writers and professional speakers. She has extensive experience in the United States and abroad with more than 35 years in the industry and is a gifted and award-winning designer who combines artistic vision with practical horticultural strategies.

 

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