No, sorry! This has nothing to do with Jerry Garcia, an icon to many in my generation. Somehow I seem to have missed that phenomenon.
I am now grateful to have some knowledge about deadheading, which is the removal of spent blossoms to prolong the flowering of many annuals and perennials.
OK, it was a blatant bait and switch trick, but you might as well read on because this is a good summer topic for gardeners who want to improve their skills.
Let’s review some basics. As you know, annual plants undergo their entire life cycle in a single growing season. Biennials have a two-year life cycle. Perennials live for three years or more – if you are lucky (Gil’s law: the lifetime of the perennial is inversely proportional to the price of the plant).
The life cycle for annual plants includes its initial growth, the formation of flowers and then the formation of seeds from pollinated flowers. Finally, the plant, its reproductive mission accomplished, fades and eventually dies. These annuals are endowed with a hard-wired determination to complete that mission. If their flowers are removed after the blossoms have faded, but before they develop seeds, the plant will often make new flowers in an effort to complete the seed-making process. It has nothing to lose; it is not trying to save resources to make a comeback the following season. It will continue to make new flowers until it runs out of resources or succumbs to frosty temperatures.
Cleome is a prolific self-seeding annual
The clever gardener can interrupt the annual life cycle by pinching or snipping off fading flowers before they go to seed — deadheading. Aside from the aesthetics of longer bloom time and tidy plant appearance, there is a third benefit. Some plants are notorious self-seeders. Unless the gardener actually wants the seeds to create new plants next season, he or she may continue deadheading until the end of the growing season. There are some prolific self-seeders; among the annuals, cleome comes to mind. The volunteers that arise the following season from these annuals may be welcome, or they may become a major weeding headache in the spring of the following year. When the next generation differs strikingly from its parent, the volunteers are usually considered weeds.
Some annuals, such as fibrous begonia, impatiens, and moss rose, need not be deadheaded because they do it themselves.
Perennials are more complicated because they have a dual mission in life: to reproduce and, unlike the annuals, to live beyond a single growing season. They do not readily play the gardeners’ game. Perennials typically do not flower as long as annuals for a reason. They are determined to come back the next year; so after they flower and set seed, they begin to store resources (e.g., carbohydrates they have produced through photosynthesis), usually in roots, rhizomes, or bulbs.
However, some perennials have a larger resource budget than others. These may rebloom after deadheading (e.g., rose, garden phlox, coralbells, Shasta daisy, veronica, delphinium, and daylilies).
Top: purpletop verbain flowering; Bottom: purpletop vervain volunteers from 2015 seeds not exactly where I want new plants to grow
Others benefit healthwise from deadheading by directing the energy associated with making seeds into growing more leaves, stems and, most important, roots. Furthermore, the spent flowers of some perennials may become disease magnets. For example, gray mold (Botrytis cineria) is known to infect the faded flowers of peony.
As with annuals some perennials are vigorous self sowers. Yarrow is one. Unless you are trying to create a bed of yarrow, it is a good candidate for deadheading. That tall, thin beauty, purpletop vervain (Verbena bonariensis), a relatively short-lived perennial, drops enough seeds to fill a nursery with seedlings. Some selective deadheading keeps the weed problem at bay while continuing the existence of the plant in the garden.
Some perennials have seed heads or berry clusters that provide winter interest (sedum ‘Autumn joy’) or valuable food for birds (rudbeckia). Deadheading these is not necessary.
Some gardeners are reluctant to deadhead their flowers because they don’t know how to do it. Deadheading is really simple. Cut or pinch off faded flowers just above the next flower bud on the stem or the first group of leaves on the same stem when there are no flower buds. For some plants, the group of leaves may be at the base of the plant. In those cases cut off the stem right above the basal leaves. Except for roses that sometimes require that you distinguish between leaves that have three leaflets and leaves that have five, that’s all you need to know.
Deadheading, a brochure produced by Penn State Extension, contains the best list of annual and perennial plants to deadhead.