April showers bring May flowers. May flowers make a mess. Well, some of them do. Most simply disintegrate and fall from the trees, shrubs and vines that produced them, and decompose into the soil below. Some might have needed to be swept off of pavement and decks. Regardless, most of us do not notice the very minor consequences for the majority of spectacular spring bloom.
However, there are some flowers that demand a bit more attention after they finish blooming. They linger after the show is over, and can look shabby as they deteriorate. Small ones can simply be plucked. Larger blooms might need to be pruned out. The process of removing deteriorating blooms is known as ‘deadheading’, and it is done for more reasons than just to keep plants groomed.
Plants bloom to produce seed, and the production of seed takes resources. Removal of seed structures not only diverts resources to more useful functions, but for many plants, it also stimulates subsequent bloom in response to interrupted seed production. They literally keep trying until they are able to produce viable seed, even if they must continue all season until late autumn dormancy.
Most plants that benefit from deadheading are perennials. Shasta daisy, black-eyed Susan, blanket flower, cone flower, yarrow, lavender and beard tongue (penstemon) bloom more abundantly and for a longer time with regular deadheading. The various lavenders, as well as other perennials that are comparably shrubby, are easily deadheaded by shearing after profuse bloom phases.
For bulbs and bulb like perennials that bloom only once annually, deadheading will not promote subsequent bloom during the same year, but conserves resources for the following year. Daffodil, lily, clivia, various iris and, during summer, gladiolus and dahlia, all appreciate diligent deadheading.
Petunia and marigold are two annuals that happen to bloom better with regularly deadheading. They bloom so profusely that deadheading can be quite a chore. Plants that can be invasive, such as salsify, should be deadheaded before dispersing seed.