Richard Bogren, Gill, Daniel J. | 7/21/2017 1:37:08 PM
By Dan Gill
LSU AgCenter Horticulturist
(07/21/17) Deadheading is an important but often neglected gardening technique. It refers to pruning off old, faded flowers from a plant as it blooms. It is most often done to annuals and perennials, but it is also useful with some summer-flowering trees and shrubs.
A number of advantages to deadheading make it worth the time and effort it involves. For one thing, it improves the appearance of a plant tremendously. Plants that bloom over a long period of time often end up with an accumulation of unattractive, dead flowers and seed pods mixed in with the newly opened blooms. This makes the plant look bad even with pretty flowers on it. If you keep the faded flowers pruned off the plant, it always looks fresh — as if it were just coming into bloom.
Removing the old flowers from many types of plants also will encourage them to bloom more and for a longer period. Annual plants, in particular, bloom for a time, set seed and then stop blooming and die. Regularly removing faded flowers prevents the plants from setting seed. As a result, annuals will respond by producing more flowers over a longer season in a continuing effort to produce seed. Many perennials will send up another flush of flowers if they are promptly deadheaded.
There are other advantages to preventing bedding plants, perennials and bulbs from setting seeds. Unless you intend to grow new plants from the seed produced, it is a wasted effort. Plants commit considerable resources to creating seeds. This effort could be redirected to growing more leaves, stems and roots, leading to a more vigorous plant and, perhaps, more flowers the next season. For annuals and perennials that self-seed, deadheading prevents unwanted seedlings from popping up all over the garden.
Depending on how the flowers are produced, deadheading may involve removing flowers on a single stem, such as gerbera daisies, removing faded clusters of flowers, as on yarrow, agapanthus or amaryllis, or removing faded flower spikes, as on snapdragons or veronica. If they are large enough, individual faded flowers can be removed from a stalk or cluster containing numerous flowers, as on rudbeckia, daylily and stokesia. As individual flowers in a cluster open and fade, they are removed, but buds are left in place to bloom. Once all the flowers have opened and finished, the entire stalk is removed.
When deadheading, always remove the stem that attaches the flower to the plant when you remove it. The idea is to remove any evidence that there was a flower at that location. Besides, headless flower stems are unattractive.
If you miss removing the faded flower and a seed pod has already started to develop, go ahead and remove the seed pod. You may still help encourage the plant to bloom longer or prevent the plant from wasting energy on further developing seeds.
If you do want to collect seeds from a plant or if you want it to self-seed in your garden, you must allow at least some of the flowers to set seed. The best way to handle this situation is to deadhead early in the flowering season and then let some of the last flowers set seed.
While you are deadheading, take the opportunity to groom your plants by removing damaged, unattractive foliage and dead stems or branches. Not only is this healthier for the plants, but it also keeps them looking their best. It is also a good time to inspect your plants for developing insect or disease problems and decide what kind of control, if any, is needed. Notice if any plants need to be staked or supported after months of growth in the garden, and attend to that as well.
A few summer-blooming trees and shrubs can benefit from deadheading. Crape myrtles, vitex and oleander are more likely to produce a second flush of flowers after the first is finished if you are able to trim back the old flowers or developing seed pods. Make your cut just behind a faded cluster or flower spike.
In a few cases, perfectly good flowers can be removed from plants. In the case of coleus and caladium, where the colorful foliage is the star, the flowers or flower buds are removed to encourage production of more attractive foliage. Flower spikes of herbs, such as basil, parsley and cilantro, are also removed to encourage continued production of flavorful leaves.
Once again, the plants that respond best to deadheading by extended flowering are annuals and perennials that bloom over a relatively long season as well as some summer-flowering trees and shrubs, such as crape myrtle, vitex, rose and oleander. Deadheading will not extend the flowering time of shrubs, such as azaleas or hydrangeas that bloom from a set number of buds, or perennials that bloom for a relatively brief season. But it can make them look more attractive and prevent them from wasting effort and energy on seed production.
Deadheading spent flowers from bedding plants not only encourages repeat blooming but also enhances the appearance of the plant. Photo by Rick Bogren/LSU AgCenter
Removing faded flower spikes from plants like this agapanthus encourages the plant to develop roots rather than seeds. Photo by Rick Bogren/LSU AgCenter
Pinching off flowers from bolted herbs such as basil encourages the plant to continue to produce foliage rather than spend energy making seeds. Photo by Rick Bogren/LSU AgCenter