Deadheading–or trimming off faded blossoms–prolongs flowering by initiating a second flush of smaller and less numerous blooms. This helps to keep a garden attractive by keeping plants neat and tidy and ensuring maximum bloom time. How and when you remove spent flowers depends on the plant and the type of growth it produces. The following list provides guidelines for typical types of growth…
Long flower stalks
Plants that produce one flower head at the end of a stalk, such as pelargoniums, should have the fading flower removed, along with the stalk – snapping it off cleanly from the stem. Bulbs, such as daffodils and tulips, are the exception. These should have the flower cut off leaving the stalk intact.
Short flower stalks
Plants that produce flowers on short stalks, such as fuchsias, should have the fading bloom removed by pinching off the stalk behind each fading flower between the finger and thumb.
Many border flowers that bear their blooms on tall spikes, such as foxgloves and delphiniums, antirrhinum, hollyhock, lupin, and penstemon, can be encouraged to produce a second flush of smaller spikes later in the year by deadheading. When the last of the flowers start to fade on the spike, simply cut the whole spike back to just above the highest side-shoot lower down on the stem. Smaller side-shoots will develop and bloom towards the end of the summer.
Many repeat-flowering plants, such as bush roses, will flower better and for much longer if regularly deadheaded throughout the flowering season. Floribunda roses (cluster-flowered) should have each fading bloom cut from the cluster until the last one remains. As this fades, cut back the cluster to just above a leaf joint, about six inches below the flower cluster.
With large-flowered, hybrid-tea roses, cut each faded bloom back to just above a leaf joint, about nine inches below the flower. By cutting back into thicker stems like this, stronger flowering shoots and a greater number of flowers will be produced. Feed roses with a rose fertilizer after the first crop of flowers have been deadheaded to encourage more blooms.
Some multi-stemmed plants which produce several flowers on stems grown during the current season can be pruned to encourage some stems to flower earlier or later than others. This method spreads the flowering display over a longer period. Clematis and other vigorous shrubs such as lavatera or the butterfly bush (Buddleja) can be cut back about two-thirds, leaving the others to flower earlier than the hard-pruned stems.
Removing the spent blooms helps to preserve the plant’s energy. This energy can be used to produce more blooms, rather than going into seed production. Deadheading also promotes root and foliage growth to keep the plant looking healthy.
This video explains the different deadheading methods: