By Cathy Krar, Master Gardener In Training, SCMG
Get out your sharpest secateurs, micro-tip pruning snips, or garden scissors and prepare to lop off stems, stalks, leaves and blooms that no longer showcase your perennials.
Deadheading helps preserve plant energy and prevents the plant from becoming weaker due to seed production. How often you deadhead depends on the variety of plant and the weather. You can deadhead flowers any time they begin to die back. Where to deadhead can be the confusing part. Generally, you can deadhead spent blooms and stems back to ¼ of an inch above a new laterally growing flower, leaf or bud.
Deadheading is most effective during the hotter summer months, when the flowers are showy, and before they go to seed. Re-seeding may result in a spread that proves to be more of a nuisance than a welcome display next season, when they run amuck into the neighbouring plants.
In order to maintain a more pleasing aspect to garden aesthetics, deadheading extends bloom time, and results in a structurally vigorous plant. It may seem harsh when you put in new plants, but it really helps to cut off the blooms. This will result in much healthier plants to display. In creating larger, fuller-looking plants, it helps them to fend off disease from fungal infection or rot. Overgrown plants typically flop over onto their neighbours causing a garden with a congested mess.
Some plants just have prettier foliage, and their appearance is maintained when their flower colour is removed. Woolly Lamb’s Ear (Stachys), Rumex sanguineus, Meadowsweet (Filipendula), and some forms of Artemisia (wormwood) for example.
Peonies can be done once a year. You can certainly just cut off the flower head, but it seems to be better to follow the flower stem into the plant and cut about ½ inch above the leaves.
Roses should be deadheaded back to the first grouping of 5 leaves. This will encourage quicker re-blooming and improve the shape and appearance of the rose. Alternately, roses that produce rose hips can be left alone, if you want hips during the fall/winter months. Don’t forget to wear your leather gloves to avoid the thorns.
Some forms of Campanula and Balloon Flowers need to be deadheaded, flower by flower. Once the bloom has stopped, the stalks can be cut fully back.
Delphinium stalks can be cut back, try by half (once 70% of their blooms are spent), until new growth is showing at the base. Wait until the basal growth is about 8 to 10 inches before removing the old foliage right to the ground. This is the best way to get your Delphiniums to bloom twice in the season.
Plants like Shasta daisy, yarrow and veronica can be deadheaded to a lateral leaf, bud or flower. When these plants no longer produce flower, they can be cut down to the base.
Biennial plants like Digitalis (foxglove) and Alcea (hollyhock) can be encouraged to behave more like perennials if you cut them about halfway down the stalk, and then to the base, once new growth occurs.
Columbine (aquilegia) should be deadheaded to the next flower, as with daylilies (Hemerocallis),Knautia, and Pincushion plants (Scabiosa).
Once the Hardy geranium bloom is done, a good tug should remove the stalk.
Dianthus can be deadheaded by pinching off the flower by hand or with pruning shears.
If you have mounding perennials like Coreopsis and Salvia, a hard pruning back to 2 to 3 inches can give these plants a fresh start once the blooms have faded. It has the added benefit of keeping them tidy, and continued bloom throughout the summer.
Always consider leaving 1/3rd of your hostas to go to seed, as well as the coneflowers for our fine-feathered friends. Cutting back 2/3rd of your blooms to prevent over-seeding.
If you use October 1st as your gauge to completely deadhead daisies, helenium, blanket flower (gaillardia) and pincushion flowers (scabiosa); otherwise, these flowers may bloom themselves to death.
Don’t be alarmed if deadheading doesn’t look cosmetically pleasing right away. Fast forward two or three weeks, should see positive rewards for your efforts.
Resources:
The Dos and Don’ts of Deadheading Flowers by Katelin Hill
https://www.bhg.com>perennials
https://www.fiskars.com
