The name of this operation — deadheading — is ominous, but it sounds far more dramatic than it is in practice. For deadheading is nothing more than the removal, with a pinch of the fingertips or a snip of the shears, of a fading flower before it can set seed. This is a common, and usually much needed, activity at this time of year, when the garden is recovering from the floral orgy of June, and it’s festooned with wilted, over-the-hill blossoms. Basic neatness demands that you remove these sad remnants. In addition, though, conscientious deadheading has a number of other benefits.
Deadheading is an essential kind of maintenance for most annuals. As the name indicates, this class of flowers completes its life cycle — growing from seed to mature plant and then bearing its seeds — all within a single growing season. A certain number of cold-intolerant perennial flowers such as geraniums and impatiens are commonly treated as annuals because they won’t survive through a northern winter, but true annuals, flowers such as marigolds, zinnias and common sunflowers, are actually genetically programed to die after they set seed. This means that if you don’t deadhead, they will decline after a single flush of flowers. If, on the other hand, you remove the flowers at their bases as they fade, you can short-circuit this cycle. If prevented from setting seed by deadheading, annuals will commonly respond by bearing a second flush of flowers, and then a third, and so on until frost cuts them down in the fall.
Deadheading can have a similar, though less potent, effect on many perennials. Trim back bushy perennials such as lavender by a third as their flowers wither, and you will encourage the plants to put on a burst of attractive new growth and a second, albeit smaller, crop of blossoms. You’ll achieve a similar effect with vertically-oriented perennials such as delphiniums, foxglove and columbines by cutting back spent flower stalks to just above a dormant bud. That will encourage the growth of a new, smaller shoot or shoots that will flower again, albeit not as impressively.
Deadheading is alleged to have other benefits as well. When practiced on perennials, bulbs and flowering shrubs, it is said to foster more vigorous growth by preventing the plants from squandering their energy on reproduction. I am dubious. I have heard of no scientific research substantiating this claim. It made me glad that I belonged to a less regimented generation when, as an apprentice gardener, I heard stories from old-timers about whole days spent in pinching fading flowers off of rhododendrons and other flowering shrubs when they were serving their apprenticeships.
One effect that conscientious deadheading will undeniably have, for good or ill, is to keep flowers from self-seeding around the garden. This may be seen as a benefit if you are growing flowers such as corn poppies, lady’s mantle or columbines that can easily become weeds, springing up all over the place. I’ve come around, however, to seeing such “volunteers” as a benefit rather than a threat. In general, I’ve found that it’s easy enough to hoe out or snip off at the base any unwelcome self-sown seedlings, while enjoying the contribution of the ones that provide unanticipated but welcome color.
In some cases, seed heads are an important element of a plant’s appeal. A few weeks ago, for example, I was admiring in a friend’s garden the whorled, brass-colored seed heads of her clematis. She praised these as an attraction fully equal to the vine’s spring-blooming flowers. Coneflowers and coreopsis also bear striking seed heads, and these serve as a source of food for seed-eating birds. A few less flowers is not much of a sacrifice to make for nurturing the wildlife.
Be-a-Better-Gardener is a community service of Berkshire Botanical Garden, located in Stockbridge, MA. Thomas Christopher is a volunteer at Berkshire Botanical Garden.