This is a common but potentially time-consuming task. For some gardeners, deadheading can actually be fun, but if you have a lot of plants to tend, it can become a daunting task, so it’s important to know which plants benefit most from this action and which can be left alone.
Simply put, deadheading prevents the plant from producing seeds and completing its life cycle. Instead of spending energy on producing seeds, it can redirect its energy into producing more flowers, extending its season. However, not all plants bloom multiple times, so in these cases the results are less obvious and are often more about tidying up the appearance of the plant.
The simple answer is that it depends on the plant. For some common garden flowers, deadheading can really make a big difference. If you don’t deadhead some flowers, they will have a short season or a prematurely wilted appearance, in which case you might be better off planting a different type of plant.
For many other ornamental plants, the importance of deadheading varies; it may be optional, completely unnecessary, or in some cases actually detracts from their value at the end of the season. There are five main reasons to deadhead:
Keeping a plant from going to seed can direct its energy towards producing more and more flowers. A good example is sweet peas, whose flowers must be picked repeatedly even before they fade if the plant is to bloom for months. In late summer, dahlias will only bloom until the first frost if the old flowers are cut off. Other plants that need to be cut off to prolong their display include buddleja, cosmos, gazania, osteospermum, felicia, viola, tagetes (African marigold) and veronica (hebes).
Some plants, such as many roses, will flower later if the spent flowers are removed. With some perennials, you can simply cut the entire plant, flowers and all, down to the ground (known as a ‘Chelsea chop’) and be rewarded with fresh foliage and more flowers. Plants that will re-bloom if the flowers are removed include alchemilla, astrantia, delphinium, geum, leucanthemum, lupins, nepeta (catmint), penstemon and Sage.
Note: Although daffodils and tulips will not bloom again in the same year, removing the flowers before seed sets will help direct energy back to the bulbs, ensuring beautiful blooms the following year.
Some plants such as azaleas, lilacs and peonies do not look good after flowering and so it is best to remove spent flowers. Roses and camellias also spread their petals widely – removing a spent flower before it falls will save time later. Plants include Pyramid bell tree And C. persicifolia produce flowers that bloom individually and produce a second flush of blooms. Removing old, faded flowers is a pain but keeps the plant looking good longer.
Daylily (Hemerocallis) blooms last only a day for several weeks. It is best to remove deadheads to keep the flowers fresh. Deadheading lavender is important if you want your plant to stay neat and fresh. This includes light pruning at the same time. Other flowers that need deadheading to stay beautiful include bergenia, hellebores, hostas, irises, and kniphofia.
Some plants can become a menace to your garden and the wider environment if you allow them to germinate. It is prudent and responsible to remove older plants before they have a chance to cause problems. Examples include alchemilla, aquilegia, buddleja, centranthus and digitalis.
In some cases, over-flowering can promote diseases such as botrytis, especially if faded petals and flower heads are left in place. This is the case with some delicate, double-flowered roses and peonies, which in wet weather can suffer from a problem known as bloom blight – the flowers fail to open and the petals become infected with a grey mould. Rhododendrons are also often pruned to reduce the incidence of fungal diseases. Some other plants, especially perennials such as pulmonaria, are susceptible to problems such as mould after flowering – it is best to prune back after the flowers have faded.
It’s best to start this job as soon as you notice your flowers are looking a little stale. If your plant blooms suddenly for a short period of time, like lilacs and some azaleas, you may only need to cut the spent flowers once, but with other plants it may take longer.
Pots of summer plants such as cosmos or tagetes (French marigolds) are best pruned daily, or at least several times a week if you want to maintain an impressive display. Perennials and roses can be pruned weekly. With most plants (sweet peas are an exception), it is not too important to do this for a while.
Again, this is very plant specific. Foundation plants, finicky floribundas and roses, and any plant with flower heads may need some detailed pruning with a good pair of scissors or pruning shears (secateurs may be too clumsy) to cut off the old flowers between the new ones. If the entire head has finished, it can also be removed, perhaps with secateurs. Larger individual flowers can often be removed with secateurs as well.
One thing to definitely avoid is leaving behind ugly stems – often seen when deadheading without tools; honestly, it’s a job half done! The one exception to this rule is with bulbs. Daffodils and tulips are best deadheaded by hand, as the stems need to be retained. For large beds of daffodils, swinging a stem across the height of the seedling is a satisfying job.
There are other times when just your fingers will suffice. Old camellias and lilies are easily plucked by hand, while azaleas can be carefully picked between your index finger and thumb.
Fortunately, some plants don’t need to have their spent flowers removed. The most common reason is that the petals simply fall off; examples include fuchsias, impatiens (busy flowers), or plants like magnolias and plumerias..
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Don’t give up structured seed head provide interest long after the flowers have faded. Examples include alliums, cynara, angelica, fennel, honeysuckle, and hydrangeas (the papery heads of hydrangeas also protect the spring shoots from frost damage).
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Don’t give up ornamental fruit tree provide colorful displays in fall and winter. Examples include roses with beautiful hips (many rambling choices), hawthorn, Iris fetus and pyracantha.
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Do not cut off the dead flower part of the plant. planted to provide food and wintering habitat for wildlife. Most of these plants should be left alone until late winter. Examples include milk thistle, amelanchier, and helianthus (sunflower).
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Don’t give up the tree you intend to plant seeds. This includes many annual and perennial plants that can be naturalized., such as Centaurea cyanus, eryngium, Verbena or any plant for which you are hoping to collect seeds for planting.
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Do not cut off the large head. flowering tree such as chrysanthemums, philadelphus, camellias or climbing roses, or where cutting dead flowers is difficult Includes tall shrubs, trees and hardy climbers.
