Extension Educator, Horticulture
Deadheading, pinching, cutting back, deadleafing - perennial plant care sounds more like martial arts than gardening. Each one of these terms refers to an important activity in the flower garden. None of them are all that complicated but knowing when and how to do them can translate into more flowers, healthier and less floppy plants and a better looking garden.
Many people are familiar with pinching mums to make them branch. The plants grow more compact and produce more flowers. Just like pinching a cute kid's cheek, pinching is done with the thumb and forefinger. Unlike a cute kid's cheek the new growth is removed. Pinching may be the removal of just the new emerging leaves or it could be down several inches to a side bud.
Pinching encourages branching because it removes the dominant bud. Consider the top bud of the new growth as the "queen" bud. Normally the "queen" bud gets the majority of the food and growth hormones. She grows and thrives. All the side buds are the "ladies-in-waiting". When the "queen" is removed, dominance spreads out to the "ladies-in-waiting". The side buds now get more food and growth hormones and they grow. Since it takes time for the side buds to get moving, pinching usually delays flowering. This delay may be to your advantage. Judicious pinching may extend the flowering season.
Are there other perennials besides mums that would benefit from a good pinch?
Asters can be treated much like mums and pinched several times before 4th of July. Pinching mums after mid-July may delay flowering too late into the fall. Or just cut asters back by one half in early to mid June. Asters can get tall and floppy so pinching or cutting back may reduce the need for staking.
Beebalm can be cut back by one half in early May to promote more compact growth. Bloom will be delayed about two weeks. Consider cutting back part of the clump. Cut back just the front half of the clump of beebalm to develop staggered height and extend bloom time. The uncut portion will bloom at its usual time and 2 weeks later the pruned front half will bloom. We can all appreciate an extra 2 weeks of bloom. Perennials that form masses respond well to the "mullet hairstyle" method of pruning.
Phlox plants can be pinched or cut back to one half at the end of May or in early June.
'Autumn Joy' sedum planted in too much shade or in high fertility soils can flop open to reveal its inner underbelly. Not a pretty site. Pinch sedum when plants are eight inches tall to develop compact plants. Flowering will be delayed a bit and there will be smaller but more numerous flowers produced.
Additional plants that respond to pinching include yarrow, Russian sage, artemisia, balloon flower, dragonhead, goldenrod, Joe-pye weed, veronica and Culver's root. Try pinching a few and see if you like the results.
Some plants do not respond well to pinching. Often these are plants with one terminal flower spike or plants with leaves in a low rosette rather than a long stem. The "unpinchables" include columbine, astilbe, delphinium, daylily, coral bell, hosta, heuchera, iris, foxglove, poppy and dianthus.
Deadheading refers to the removal of old flowers once they are past their prime. For many perennials such as bellflower, daylilies, salvia, phlox, coneflower and yarrow deadheading will prolong bloom or encourage the plant to rebloom. Deadheading also keeps down over zealous plant reseeding.
A couple of excellent references for perennial flower care include The Well-Tended Perennial Garden by Tracy DiSabato-Aust and Caring for Perennials by Janet Macunovich. Get personal and pinch a few perennials.
Check out UI Extension websites Gardening with Perennials http://urbanext.illinois.edu/perennials/
Stepping Stones to Perennial Garden Design http://web.extension.illinois.edu/gardendesign/