Deadheading

by Bryan Fischer, Curator, and Horticulturist, Gardens on Spring Creek

What if I told you that your garden is full of deadheads right now? Gathering in large groups, they are bound to hang out for a while, emanating whispers of “flower power” unless you do something about it. 

Fortunately for you, you can behead these deadheads. The act won’t constitute homicide, and it will even serve to extend the floral display in your garden beds.  For most plants, the point of blooming is to produce seeds and thus reproduce. Since this takes a lot of energy from the plant, there’s no point in continuing to bloom once the seed is produced – so ends the flower part of your flower garden. So, regular removal of blooms that are losing their colorful, vibrant appearance prevents seed set and helps to extend the total length of bloom for many plants. This practice is routinely employed on annual plants, which are most often planted for a season-long display of flowers. 

When it comes to perennials, the use of such practice falls into a grey area. Observe how perennials behave in your landscape; those that self-sow too vigorously or look ratty after bloom are natural choices for deadheading. I don’t deadhead many of my perennials, since stems left standing over winter make ideal places for many native and beneficial insects to overwinter.

Most plants can be deadheaded in one of three ways. For those that produce flower stalks with no branching, it is best to let the whole stalk finish the majority of its display before cutting it back to the base of the plant (Delphinium, for example). For flowers producing branched stalks, cut each spent flower’s stem back to where it meets the main stem (like Rudbeckia, or black-eyed-Susan). Only after the main stem has spent all of its buds should it be cut back to the plant’s base. Finally, a minority of plants produce many flowers in a cluster, each with its own short branch, like daylilies (Hemerocallis). Deadhead these simply by picking such flowers off the stem. 

A minority of perennials like Salvias in the meadow hybrid group (think ‘Caradonna’ and similar), lady’s mantle (Alchemilla spp.), and some Nepeta spp./cv. (catmints) benefit from a hard cutback after bloom; this will refresh the foliage and often result in a second, lighter bloom. Such a hard cutback can be at or near ground level and will replace the need for deadheading. In general, if an entire plant is looking tattered, splaying, or beat up and the floral display is finishing, this practice is worth a try. Don’t employ a hard cutback on woody plants so casually, and don’t practice this technique after the month of July to ensure plants aren’t stressed or tender as they approach cold temperatures. 

Regardless of what you may choose to deadhead, use a sharp pair of bypass shears, sometimes called “snips” in the trade, and make cuts at a 45-degree angle. Avoid, too, deadheading plants you want to increase in the garden by seed since by nature the practice prevents seed development. Deadheads typically aren’t the garden menace they were once considered, and many foster beneficial insects and provide food for birds and other wildlife. Not as widely employed as it once was, the practice still has merit and use in some gardening styles and with some plant materials. You should know how and when to use it!