Deadheading doesn't guarantee new blooms on your flowers

  • At this time of the year, you can deadhead coneflowers to tidy up your garden, but experts at Morton Arboretum say you shouldn't expect a fresh round of blooms.

    At this time of the year, you can deadhead coneflowers to tidy up your garden, but experts at Morton Arboretum say you shouldn't expect a fresh round of blooms. Bill Zars | July 2008

 
Published8/18/2008 12:18 AM

Things are looking a little shaggy around here lately, and I'm not just talking about my teenage son's summer haircut. The coneflowers near our doorway are becoming skeletal, the monarda moldy and the day lilies desiccated.

I'm not ready to give up. I want one more show before sending my garden to the dog days of summer.

 

Pinching, deadheading, cutting back. All these somewhat barbaric sounding techniques can be used to encourage bloom. To revive your garden in August, such methods may work. But what plants respond well to pinching and which should be cut back? What's the difference?

"Pinching is a way of controlling the rate of growth of a plant," said Abbie Rea, Morton Arboretum's assistant manager of horticulture. "It's used more to control the overall shape of a plant."

When you pinch a plant, you remove the tip of the central shoot, often down to where there are only two to three sets of leaves near the base. The goal is to produce a bushier plant. "Generally, you're going to be finished with pinching by the end of June," Rea said.

Pinching is pretty much out of the picture then, for August, because plants will not have enough time to respond as the growing season ends.

It's actually a misnomer to uses phrases such as "pinching petunias," according to Rea, when what is really meant is deadheading.

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Deadheading comes in two forms; plucking off the spent blooms of flowering plants such as petunias, or cutting back hard. The first is a form of maintenance, a cleanup of the garden to keep it looking tidy. Cutting back hard, the second form of deadheading, like pinching, is done to promote another flush of growth. On some plants, cutting back hard can be done now to produce more foliage and flowers before the first frost.

Many annuals and perennials can be cut back hard in late summer. After a plant has bloomed, and as it starts to become floppy or ragged looking, cut about one-third of the plant's stems one-third of the way down. "It will reflush with foliage and light flowering," says Rea.

Not all plants respond to cutting back; some will not produce new foliage at all. Check the base of the plant for new sprouts or stems - although not guaranteed, this is a likely indicator that the plant is a good candidate for cutting back. If so, "cut the plant fairly close to the soil line, give it water, compost or mulch," advises Rea.

Plants that respond well to cutting back - and will produce another flush of foliage and some blooms - include perennial salvia, lady's mantle, iris, rudbeckia, monarda, meadow-rue (thalictrum), yarrow, catmints and many other herbs.

                                                                                                                                                                                                                       
 

"Echinacea does not have a strong rebloom," Rea warns, "so don't plant it where you'll be seeing vast sweeps of brown (spent plants) for awhile."

Darn. That would include my front entryway. To hide the brown areas, Rea suggests some good companion plants for these coneflowers such as prairie dropseed and other grasses. Other plants, such as hosta, benefit from deadheading the scapes, but don't expect more flowers or foliage.

Many day lilies are sprouting seed pods right now, and Rea says it's a good signal to do some deadheading. Unless you want the seeds for some reason, cut the stalk and pod and let the plant put its energy into producing more foliage. Cut the spent foliage to the ground, top dress with compost and water, and you can expect another flush of foliage this year.

When is it really time to stop all this deadheading and cutting back?

"Generally plants and perennials do grow through October," Rea said, "so cutting back through mid-September is OK."

Then I guess it really is time to close the books on this summer and welcome in the fall.

Cathy Maloney is an avid gardener and a writer for Morton Arboretum. Her column runs monthly.

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