To "deadhead" plants means to remove their spent flowers. For many plants, removing the blooms after they have gone by promotes more flowering on them for that year than would occur without such plant care. Gardeners also take the old blossoms off simply to keep ugly, shriveled-up flowers from marring the appearance of a planting bed. Yet another reason to bother with this chore is to keep unwanted seedlings from popping up in your yard; for example, you can keep nuisance seedlings from rose of Sharon (Hibiscus syriacus) in check through deadheading.
How to Deadhead a Plant
For soft plants, you can deadhead by hand (although it still helps to have long fingernails), pinching the stem between your thumb and forefinger. For those with tougher stems, you may need pruners to make your cut. Be sure to remove the entire flower. Many beginners make the mistake of removing just the petals, missing the part of the flower where the seeds are actually forming (which defeats the main purpose of deadheading).
"Deadhead" and "pinch" are very similar terms. Some people use them interchangeably. Others make a technical distinction, insisting that you "pinch back" a plant before it flowers, to make its vegetation bushier; whereas you can only "deadhead" a plant, by definition, after it has flowered (since it is the "dead" flower "heads" that you are removing).
You do not always have to be fussy about the operation. Some plants can be sheared to yield the same effect as deadheading, in the long run. For example, give your sweet alyssum (Lobularia maritima, the short plant often used as an annual ground cover) a good haircut with a pair of scissors to make it re-bloom. It really depends on the type of plant you have.
Be more careful with a tall perennial that has long, leafless flower stems. For that type of plant, you would deadhead by removing individual flower stems once the flower or flowers have passed (since, being totally bare now, the leftover stem would be unsightly if allowed to remain). For other plants, a good place for a cut may be down to a place on the stem where there is a lateral leaf.
Promoting Re-Blooming by Deadheading: How It Works
Deadheading to produce more flowers is basically about channeling a plant's energy into a direction that you find more agreeable than the "natural" direction. When you deadhead flowers, you are channeling energy away from seed production and into further flower production. In essence, to "deadhead" a plant is to trick it into forming additional flowers, in its attempt to (finally) produce the seed it set out to produce in the first place before you deadheaded it.
Think of it this way. The plant's game plan is to reproduce by forming seeds. This conflicts with your own plan, which is to enjoy flowers for as long as possible (once they go to seed, the floral show is over). You, as the gardener, have the right to tell your plant (by deadheading it), part-way through the game, "Hey, plant, I am overriding your plan: You will be waiting a bit longer to form those seeds." Do not worry: The operation does no harm to the plant. In fact, both parties should be quite happy with the results.
After a plant has been deadheaded, the second blooms typically last longer than the originals. That's because deadheading encourages the plant to strengthen itself rather than to produce seed.
Plants You Should Deadhead
Not all plants need to be deadheaded. But it is generally a good idea to remove the spent flowers from your annual plants if you wish to achieve the best landscaping with four-season interest. Deadheading gives many of them the chance to continue blooming throughout the summer and, in some cases, right into the autumn (annuals thus treated can expand your fall-flower choices).
Sometimes, a plant cries out to have its flowers removed, so that the decision on your part is a no-brainer. For example, petunias look horrible after a rainstorm. This provides the perfect excuse to deadhead them.
Many perennial flowers, too, profit from the operation. Repeat-flowering rose bushes (such as hybrid tea roses and floribunda roses) are examples of shrubs that you should deadhead if you want more blossoms from them.
Without deadheading, some annual flowers will peter out prematurely, robbing the landscape of the color they can provide in late summer and/or early autumn. And the comparatively short blooming season of some perennials can be extended if you deadhead them.
Plants That May Flower Longer With Deadheading:
- Avens (Geum spp.)
- Bee balm (Monarda didyma)
- Butterfly weed (Asclepias tuberosa)
- Columbine (Aquilegia spp.)
- Foxglove (Digitalis spp.)
- Garden cosmos (Cosmos bipinnatus)
- Garden phlox (Phlox paniculata)
- Geraniums (Pelargonium)
- Hollyhocks (Alcea rosea)
- Italian bugloss (Anchusa azurea)
- Larkspur (Delphinium spp.)
- Lavender (Lavandula spp.)
- Lupine (Lupinus spp.)
- Marigolds (Tagetes spp.)
- Monkshood (Aconitum spp.)
- Mountain bluet (Centaurea montana)
- Rose campion (Lychnis coronaria)
- Salvia (perennial)
- Shasta daisies (Leucanthemum x superbum)
- Speedwells (Veronica spp.; the kinds that produce flower spikes)
- Tickseed (Coreopsis spp.)
- Wild violets (Viola odorata)
- Yarrow (Achillea millefolium)
Plants You Don't Need to Deadhead (or Should Not)
This list is a bit more complex because you must consider three factors:
- Some perennials simply won't bloom again whether you deadhead or not.
- Some perennials don't look messy after they've finished flowering, so you needn't worry about cleaning them up.
- In other cases (indicated by an asterisk), not only will the plant not re-bloom, but you positively should avoid deadheading so as to allow attractive seed heads to form and remain in place for winter interest.
Examples follow; each falls into at least one of these categories:
- Autumn Joy stonecrop (Sedum spectabile) *
- Barrenwort (Epimedium)
- Goat's beard (Aruncus dioicus)
- Joe-Pye weed (Eupatorium)
- Leopard plant (Ligularia dentata)
- Peony (Paeonia)
- Siberian bugloss (Brunnera macrophylla)