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updated: 7/3/2014 5:53 AM

Three alphas for the dog days of summer

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  • Liatris elegans, which are native to the Southeast below North Carolina, have tall flower spikes that tend to flop.

    Liatris elegans, which are native to the Southeast below North Carolina, have tall flower spikes that tend to flop.
    Lisa Roper/Chanticleer garden

  • Liatris aspera has a looser inflorescence and button-like flowers.

    Liatris aspera has a looser inflorescence and button-like flowers.
    Lisa Roper/Chanticleer garden

  • Coneflowers, as a rule, like well-drained and somewhat impoverished soil that is not too acidic.

    Coneflowers, as a rule, like well-drained and somewhat impoverished soil that is not too acidic.
    Washington Post photo by Adrian Higgin

By Adrian Higgins, The Washington Post

If the world cleaves into two types -- restless thrill-seekers and those who cling to the familiar and safe -- I suppose I fall into the latter group. But if you've found something that works, why not stick with it?

Years ago, I discovered that the July garden can be elevated from its drab lassitude to something dreamy and fun by getting three high-performing perennials to play together, namely the perovskia, the coneflower and the liatris. By mixing them together, rather than planting in discrete blocks, one can convey a summery cottage garden atmosphere to sunny beds. The show begins now and lasts for weeks.

They are robust in size and spirit during the hottest month of the year and can be counted on to provide a prolonged and effective flowering display when other plants are mopping their brows. The violets of the perovskia may clash a little with the magenta-purples of the coneflowers, but given their show and given the weather, this dissonance is fine.

To most of us, the coneflower is a sturdy purple daisy, somewhat muddy in hue, with petals that extend out and down from a domed, central coppery orange disc. But it is one of those perennials that has grabbed the imagination of plant breeders and, just as importantly, the nursery trade, resulting in a slew of fresh varieties that have ventured into novel and better colors. Using another native echinacea species, the yellow coneflower, they have produced versions in eye-catching yellows, reds and oranges.

Normally, such hybridization produces a more vigorous growth. Alas, many of these varieties seem to be short-lived, perhaps because they are even fussier about drainage, particularly during winter dormancy. Coneflowers, as a rule, like well-drained and somewhat impoverished soil that is not too acidic. A few new varieties and hybrids, though, have been given high marks by horticulturists in the Mid-Atlantic region, including Sunrise (lemon yellow), Hope (a clear pink) and Tiki Torch (orange). If you like white coneflowers, Coconut Lime and Fragrant Angel are commended by those who grow them. The latter has a more graceful form, to my eyes.

I prefer the standard purple coneflower, particularly two established cultivars -- Magnus, bred for its large flowers, and Leuchtstern, redder in hue and earlier to bloom.

Perovskia, or Russian sage, has been a stalwart of the summer garden for decades. Large and ethereal, it is a study in contrasts. Its violet-blue flowers twinkle amid the ghostly white stems. For all their petiteness, they create a haze that can be read from hundreds of feet away.

Perovskia's fragrance is pronounced, pungent and not entirely agreeable. It has greater flaws. The wiry stems tend to wander, if not flop, even in full sun. And its color is sapped by our heat. Gardeners in northern regions find it lacking here by comparison.

Several varieties have been introduced. Filigran is said to have better color in the heat. Blue Spire has finely cut leaves that are keenly attractive in their own right.

But if the coneflower has been overbred in some respects, perovskia has been neglected by hybridizers, especially when you consider the importance of its role in the summer garden. Little Spire is a recent introduction that seeks to address the compactness issue. It grows to about 30 inches, maybe half the size of a mature, sprawling specimen.

For all our cravings for more, the perovskia has to rate as one of the most useful perennials in the garden. Although it peaks in July through August, it continues to bloom into the fall, as well as adding a lacy texture to flower beds.

Some of my oldest specimens have become woody at the base, like an old lavender, but are still showy after more than a decade (and without dividing). To keep them in check, I cut back the spring growth by a half or more by June. This delays blooming a little but makes for a neater, bushier plant.

Liatris blooms on an extended spike, a raceme, that makes its flowering period long and lovely. This is why florists like it, as do wildflower fans. It is a plant of meadow and prairie, whose vernacular names include blazing star and gayfeather. It also makes a great garden plant, providing a vertical accent that is treasured in a steamy climate that denies us the displays of delphinium and eremus.

There are a dozen or so species of liatris, but the one most common in horticulture is Liatris spicata, which is stout and showy. I grow the variety Kobold, selected for its long period of bloom on multiple flower spikes. A white version, Floristan Weiss, is much admired.

Other liatris species deserve more use. Lisa Roper, the horticulturist of the Gravel Garden at Chanticleer, in Wayne, Pa., particularly likes Liatris aspera, which has a looser inflorescence and buttonlike flowers. Another species named dwarf blazing star (L. microcephala) should be in every sunny garden. It grows to just 18 inches, has loads of pink-purple blooms and, best of all, finely textured foliage that looks like grass.

"That's great for the front of the border," said Roper, who grows it with thyme and lavender. She also likes to grow liatris varieties with eryngiums, as well as grasses such as calamagrostis and nassella.

Roper also commends Eureka, a variety of a species named Liatris pycnostachya. It has lanky, flower-filled stems that need staking to prevent flopping.

One of her favorite gayfeathers is Liatris elegans, which is native to the Southeast below North Carolina. It, too, has tall flower spikes that tend to flop. It is reliably hardy in the Mid-Atlantic region, especially in soil that drains well in winter. It blooms well into September. Finding a source for this liatris might be a challenge, but worth it. "They are beautiful," she said.

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