They like full sun or very light shade and well-draining soil. They bloom all summer, make striking cut flowers (whole bloom or cone only), and draw butterflies, bees, and birds, especially goldfinches.

And coneflowers are tough. They can take a long dry spell and are pretty resistant to pests and disease - most of the time. Piatt has the stunning yellow Echinacea paradoxa in his home meadow and swears deer won't touch it.

But if lunchtime's looming . . .

At Mount Cuba last week, there were yellowed leaves and other signs of an incurable, virallike scourge called aster yellows. It's spread by the aptly named leafhopper and is decidedly worse when it's cool and wet.

Spring of 2009, anyone?

Piatt, who last studied asters and next will address coreopsis, suggested that a more diverse home garden would offer better protection against pests and disease. A test garden, with hundreds of plants of only one kind, is "an artificial environment," he says.

Still, a sea of sunny coneflowers is quite a sight.

"They're very nice and very popular," says Albert Ligameri, manager of Garrisdon Garden Center in Clementon, who sells a lot of the standard purple coneflower, along with 'White Swan' and 'Magnus.'

But yellow is a strong crowd-pleaser.

"We have one. . . . Its cone is up and the petals go downward, kind of like a Mexican hat in a way, very unusual. People like that a lot," Ligameri says.

Catherine Smith, owner of Redbud Native Plant Nursery in Glen Mills, prefers the old classic, Echinacea purpurea, for its wildlife-friendly seeds and nectar, and its classic beauty. "It's gorgeous in a meadow," she says.

That's Lovitz's favorite, too.

"The point of my garden is butterflies and hummingbirds and wildlife," she says, "and I know they come to these beautiful purple ones."

A Plant Breeder Talks in Del.

James Ault, director of environmental horticulture research at the Chicago Botanic Garden since 1995, will discuss his plant-breeding program at a Coneflower (Echinacea) Field Day at Mount Cuba Center from 3 to 6 p.m. Thursday. The center is located at 3120 Barley Mill Rd. in Hockessin, Del.

Ault, formerly plant propagator at Longwood Gardens in Kennett Square, is credited with producing the first-ever orange coneflower, called 'Art's Pride.' He also works with baptisia and phlox.

The field day program includes a presentation on the Mount Cuba coneflower study by Vic Piatt, trial area gardener, and Jeanne Frett, horticultural research manager, a tour of the trial garden, and a free coneflower.

To register, call 302-239-4244 or go to http://www.mtcubacenter.org/. Fee: $15, includes refreshments.

Contact gardening writer Virginia A. Smith at 215-854-5720 or vsmith@phillynews.com.