After the flowering party is over…
Their blooms have come and gone and left behind are the fallen petals and the swellings and bulges not unlike those at a mom-to-be convention. After the flowering party is over for many annuals and perennials, a gardener’s task turns to deadheading the finished blooms. The newly forming seed heads need to be removed by pinching, shearing or just plain pruning them out.
For some plants, deadheading is done to improve visual appearance. By removing the finished blooms the plant looks a lot better. Butterfly bush, ageratum, artemisia, Pelargonium (annual geranium), gazania, Solanostemon (coleus), and Rudbeckia (black-eyed Susan) fall into this category. Besides these, many plants that have white flowers will turn an unsightly brown colour when they are finished blooming. White blooming ageratum is one plant that often needs deadheading to make it look better.
Other plants are deadheaded for cultural reasons. Mainly to encourage more blooming. Removing the spent flower will stop energy being wasted on seed production. And still other plants have their reproductive structures removed to reduce the number of offspring that might appear the following year. The perennial, lady’s mantle is a plant that loves to “go forth and propagate”. It self-seeds like crazy. It must be sheared after the chartreuse coloured flowers are finished to prevent hundreds of babies sprouting. Some flowers are deadheaded to protect the plant’s health. The fungal disease called Botrytis likes to live on decaying flower petals. Removing the spent flower will remove the host infection site and often reduce the amount of infection.
Deadheading annuals and perennials can be done with many different tools. The simplest is the thumb and finger (or fingernail) method. Your handy digits are useful for taking the finished blooms off soft-stemmed plants such as begonia, Cleome (spider flower), marigolds, geraniums, lantana, nasturtium, petunia, salvia, or zinnia. These plants all have thin brittle stems that can easily be snapped to remove the seed heads. Hand pruners, scissors or a pocketknife is needed for plants that have a slightly tougher flower stalk. Columbines, cannas, iris, daylilies, Nicotiana (flowering tobacco), sunflowers, or heliotrope must be cut off by using pruners.
Some annuals and perennials have a habit that allows for efficient deadheading with the use of hedge shears. A sculpted effect can be obtained through skilful pruning during this process. Hedge shears can be used to deadhead plants that have their blooms all at the terminal points. Trailing or edging lobelia, perennial and annual alyssum, candytuft, lady’s mantle, dianthus, and lamb’s ears could all be deadheaded using hedge shears.
Although removing the seedpods from plants is a recommended practice, there are some instances when the seeds are left on to fully mature and ripen. If open-pollinated seed is being kept for harvesting then the seed pods must stay on the plant until they are ripe. Other plants that have decorative seedpods should be left on so that the pod can fully mature before it is harvested. Nigella (love-in-the-mist), poppies, Lotus, many clematis, and Allium are three plants that form very decorative seedpods.
There are some plants that do not require deadheading or are self-cleaning. These are great plants for a low maintenance garden because they do not require any laborious attention. Fibrous begonia, Bergenia, impatiens, lobelia, Catharanthus (Madagascar periwinkle), sunshine impatiens, and verbena are all members of this “no deadheading required” group.
Many annuals (and quite a few perennials) must be deadheaded to keep them blooming longer. Notorious are Antirrhinum (snapdragon), canna (only remove the spent flowers and be wary of cutting off future flower buds lower on the same stalk), delphinium, Heliotropium (heliotrope), Hemerocallis (daylilies), lantana, Lavandula (lavender) Liatris, nasturtium, Nicotiana (flowering tobacco will self-seed but not quite enough to create a crisis), salvia, Tagetes (marigolds), tuberous begonias (female flowers only), viola, and zinnia. Many older variety petunias would benefit from a deadheading but who has the time for this tedious work?
There are some plants that should be deadhead at all costs to avoid self-seeding the following year. This group contains the plants that are prolific self-seeders and are an inconvenience in almost every instance. These plants include: Mirabilis (four-o’clock), Cleome (spider flower), Nigella (love-in-the-mist), Antirrhinum (snapdragon), Verbena bonariensis, Melampodium, Verbascum, Echinacea purpurea (purple coneflower) Corydalis lutea, and Eschscholzia (California poppy). If this group of annuals and perennials were left to self-seed, the following year the garden will be filled with seedlings. There is a saying that one year seeding equals seven years weeding.
This last group of plants are the ones that readily self-seed, but these plants have seed structures that do not permit any deadheading to take place. Use these plants in the garden with caution unless you prefer a groundcover-like planting the following year. Talinum (jewels of Opar), portulaca, cosmos, and Lobularia (sweet alyssum) all usually evade deadheading. Each of these plants has many tiny seedpods that would require endless, finicky deadheading.
When deadheading annuals and perennials it is important to recognize what the seed head looks like so that the flower buds are not inadvertently removed. Often the flower buds will be in the terminal growth, while the seedpods will be found along older growth. Annual phlox is tricky to deadhead because there’s little difference in look between a forming flower bud and a finished seed head. Canna is tricky because if the spent flower is pruned too far down the stem then the next flower bud is removed too. During deadheading, be wary of stinging insects that like to frequent flowers. Grabbing a canna bloom to deadhead it and finding an angry bee is not a pleasant experience.
Some plants do not flower any longer even if they are deadheaded. So why waste the effort to do this task? This group includes astilbe and oriental poppy.
On a final note, some plants that have silver foliage are prone to deterioration once they have bloomed. Deadheading will allow the plant’s energy to stay directed toward foliage production. Lamb’s ears and artemisia are two key perennial plants that have this unusual habit.