AT HOME MAGAZINE

Exceptional perennial varieties keep a garden fresh, interesting

The long-flowering native purple coneflower emerges in June. Other coneflowers await the curious gardener. MUST CREDIT:
The long-flowering native purple coneflower emerges in June. Other coneflowers await the curious gardener. MUST CREDIT: Washington Post photo by Adrian Higgins
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Almost everything we encounter in life has three stages - anticipation, experience and memory.

Of these, anticipation is the most satisfying, one could argue, because it fills us with all the joy of the achievement with none of the subsequent failure or regret. Here, on the threshold of the growing season, the gardener salivates over the prospect of trying new plants.

How does one elevate the experience to the level of anticipation? One way is to be discerning not just in the type of plant selected, but also in its variety. Not all varieties of the same plant are equal, and one that performs well in one locale may flop in another. It pays to be picky and, as those old product labels used to bleat, accept no substitute.

Take the purple coneflower, one of the champions of the sunny perennial garden. There are a few cultivated varieties worth planting. Magnus is commendable - vigorous, perky and a strong rose-pink color. But many of the fancy colored hybrids, in reds, oranges and yellows, have proven poor performers, melting away like the Scotch mist.

In a three-year study of coneflower varieties, horticulturists at Mt. Cuba Center in Hockessin, Delaware, tested more than 40 varieties, giving Magnus a high rating but evaluating a few as even better, including Pixie Meadowbrite, short and floriferous; Elton Knight, with vivid magenta flowers and clean dark green foliage; and Fatal Attraction, tall, statuesque and scented. The coneflower is superb - its black seed heads haunt the garden in autumn and winter - but pick the right one.

The purple coneflower (Echinacea purpurea) is the standard-bearer, but a couple of its cousins deserve more use, including the pale coneflower (E. pallida), whose thin petals droop down from the central cone agreeably and dance in the breeze. A variety named Hula Dancer blooms extravagantly.

Another species of distinction and underuse is E. tennesseensis, a perfect coneflower for dry sites and distinguished by discrete, outstretched petals, an effect somewhere between the other two coneflowers. These plants were heartily commended by Jared Barnes, an assistant professor of horticulture at Stephen F. Austin State University in Nacogdoches, Texas.

He’s also a big fan of the black-eyed Susan’s big brother, Rudbeckia maxima, a towering daisy that will take a range of soil conditions, including wetness. There are no cultivated varieties that I know of. They are spindly, so plant a group of them. Barnes wants us to grow another sculptural native perennial, the eryngium known as rattlesnake master, and asks: “Why don’t we all have this plant? I just planted 70.”

He was speaking to an audience late last month at a symposium in Baltimore, organized by the Perennial Plant Association and the Horticultural Society of Maryland.

If you have a sunny and free-draining site, penstemons are elegant and long-flowering perennials that tend to draw hummingbirds and other pollinators. Some dislike humid summers and hard winters, but the key to their survival is to give them free-draining soil, especially during winter dormancy. Don’t plant them in heavy clay or smother them in mulch. The one you are most likely to see on the East Coast is Husker Red, a variety of Penstemon digitalis. Barnes suggests another variety, Pocahontas, which has Husker Red’s maroon stems and foliage but with lavender pink flowers instead of white.

Penstemons are like salvias; a whole world of species and varieties awaits the curious. Barnes advises East Coast gardeners to avoid species from the high, dry Rockies and to pick ones from hot, humid states. He suggests a species named Penstemon tenuis, which can take wetter conditions and produces a cloud of violet-purple blooms in late spring. Then there’s P. murrayanus, a lanky orange-red penstemon with coarser leaves that’s an absolute magnet for hummingbirds, Barnes says. Some of these penstemons are tricky to find, but you can get seed from various sources. Most will germinate willingly in seed trays and, once in the garden, will flower heartily in their second season, within their comfort zone.

The Stokes aster is one of my favorite summer perennials and grows happily in hot, humid conditions. It forms robust clumps smothered in fluffy daisies. The bare bases would benefit from some low-growing companion, cranesbill or leadwort, perhaps. Why Stokes aster isn’t more used is a mystery. The variety Peachie’s Pick is widely favored for the size, quantity and endurance of its blooms.

At the symposium, New York landscape designer Hanna Packer brought her own palette of underused perennials. In addition to her work, she also assists the Dutch designer Piet Oudolf in his North American projects, not least in finding large quantities of the precisely specified varieties that are the hallmark of an Oudolf feast of perennials and grasses.

We are thick here in the art of intensive combinations of plants, where forms, textures and stages of growth form a four-dimensional canvas. In images from a New England garden, Packer offered a series of mouthwatering combos. Molinia grass, variety Moorhexe, was used as an accent among masses of the savory calamint. The latter forms plumes of foliage frosted with thousands of tiny white flowers that bloom for weeks.

Another fabulous grass, Eragrostis spectabilis, was paired with Iris prismatica, a native bog iris that isn’t much seen in commerce. The grass, happily, is more common. It is low-growing, fine-textured and with hints of purple in its inflorescences.

One perennial that is commonly available and universally liked is the threadleaf bluestar, Amsonia hubrichtii, which sports powder blue blooms in spring but is most valued for the fine texture of its foliage and golden coloration in the fall. I’ve seen it effective in block plantings, or you might use it as an accent plant - say three in a field of low-growing grasses. Oudolf pairs it this way with the prairie dropseed, a superb, clumping, fragrant native grass whose only fault is that it takes three or four years to reach a mature size. While you are pulling the interloping weeds, the anticipation will be rapturous.

Gardening tip:

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Shredded mulch - bark is more durable than wood - should be no more than three inches thick and kept well away from the trunk flares of trees. Mulch “volcanoes,” while common, are injurious to trees and to be avoided.

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