Generally, even the best perennials bloom for only a few weeks each season. But savvy gardeners have learned to trick plants into extending their bloom period a bit longer through a technique known as deadheading.
Although it sounds threatening, deadheading is not harmful to plants. It’s simply the removal of mature flowers that are turning brown or losing their petals. Left to nature, most of these spent flowers will develop seeds. When they ripen, the plant starts to decline in preparation for dormancy and next season’s growth. Deadheading interrupts this natural cycle, encouraging plants to continue to produce new buds, which prolongs the plant’s blooming period—and that means more flowers for your garden.
Deadheading techniques vary depending on the growth habit of each type of plant. The spent flowers of most perennials can be pruned back to a new bud or leaf axil, which appears lower down the stem. These include bellflowers, columbines, coneflowers, phlox and Shasta daisies. To deadhead, use a pair of sharp garden scissors or secateurs to snip off the stem of the dead flower about half a centimetre above the next flowerbud, if one has formed, or where the next pair of leaves joins the stem of the plant if there are no buds.
The blooms of other types of perennials, including coralbells, torch lilies (Kniphofia hybrids) and thrift, grow at the top of long stems. These should be cut back right down to the base of the plant.