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Summer Blooming Perennials

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Summer is the season for long-blooming perennials. Spring perennials go in and out of bloom in rapid succession, bringing almost daily changes to the garden, especially when mixed with Spring-blooming bulbs and shrubs. In the long, warm days of Summer, everything seems to stretch out. Perennials in-bloom when you go on vacation are generally still blooming when you get back, especially after they have been in the ground for a couple of years and are established.

Summer is also the time for American native perennials. Most of the common Spring-blooming perennials are from elsewhere, often alpine locations. In Summer, the perennial flowers and grasses of the American meadows and prairies are well-represented in the garden, supplemented by non-native workhorses such as Perovskia, the Russian Sage (which sounds more like a character in a Chekhov play than a plant, if you are in the right mood), and nepeta, the catmints.

Many of these Summer plants bear yellow or golden flowers, and are members of the Asteraceae, or daisy family. That brings some challenges to the gardener to provide contrasting colors and form. Many of you are serendipitous gardeners who wander the perennial department, selecting blooming plants that strike your fancy (about 95% of you, we are told), and you shop most frequently in Spring; thus, your gardens tend to be heavily weighted in Spring-blooming perennials. We suggest you try to visit several times during the Summer to see what’s “Blooming at Behnke’s.” This will make it easier to find a selection of different colors and textures for your Summer garden.

Some thoughts on the claim “blooms all Summer.” You frequently see this term used, and it can be misleading, beyond the fact that horticulturists sometimes, ummmm…exaggerate.

First, many plants have a longer bloom period further north, where (oft times) the Summer evenings are mercifully cooler and less humid than here, and where many garden catalogues, books and magazines are written.

Second: in order to encourage longer blooming, you may need to deadhead (remove spent flowers before they go to seed) or shear the plant back to encourage a second wave of blooming* —so you may have blooms throughout the Summer, but not necessarily continually. Frequently, the initial bloom will be spectacular, and the re-blooms will be more sporadic or less showy; fewer or smaller flowers, perhaps the colors will be less intense due to Summer heat.

Third: some perennials that flower their little green hearts out often die over the Winter. Scabiosa ‘Butterfly Blue,’ Gaillardia, and Verbena ‘Homestead Purple’ are examples. Either they don’t make proper preparations for Winter, or they need super drainage, or they aren’t quite Winter hardy; or a combination of factors. We call these “short-lived” perennials. They will give you a great show, are terrific in containers, but deep down they really want to be annuals.

Some groups to consider follow: additional groups have been left out for space concerns: Phlox, Rudbeckia, Helenium and Heliopsis, for example. Author’s prerogative. Coreopsis or Tickseed; daisies that come in a variety of colors, mainly yellow to golden, pink, and two-tone pink and white. They have a long-blooming period, starting in late Spring to early Summer, and continuing to frost. Shear or deadhead to force the plant to make new flower buds.

There is much variation in the Winter hardiness of Coreopsis cultivars, and there have been many new introductions over the last couple of years. Some good rules of thumb for daisy-type flowers are that they generally perform best in full sun, and require good drainage. That certainly holds here: they often rot out in soggy Winter soils. We have had difficulty overwintering some of the new cultivars in pots (‘Snowberry’; ‘Crème Brulee’; ‘Pinwheel’, from which we infer that they will do better on a slight slope or in a raised bed than in clay-soil gardens.) While pale yellow ‘Moonbeam’ is the standard, two-tone ‘Sweet Dreams’ and ‘Autumn Blush’ are vigorous, taller and produce more blooms.

Like Coreopsis, there have been many new Echinacea introduced over the last couple of years, extending the color range of this daisy-like flower from white and shades of pink into gold, orange and burgundy; even some doubles. Purple coneflower remains the common name. The older cultivars such as pink ‘Magnus’ and ‘White Swan’ are tough as nails. Our experience and word of mouth in the industry is that some of the new hybrids seem to be harder to get through the first Winter, so watch the drainage, plant early in the season to get established, and if they continue blooming into September, remove the flowers so that the plants can prepare for Winter. Look for flowers beginning at the end of June.

Hardy hibiscus begin blooming in early July, with huge flowers in white, pink, red or bicolors. They flower continually into September, with each flower lasting one day. Recent releases have yielded shorter cultivars, as short as 30 inches, and cultivars with reddish-purple foliage. Given the plant’s coarse texture, the height of most cultivars, and the foliar shredding caused by their annual bout with Japanese beetles, they are generally used as background plants. Probably the best white bloomer, ‘Albert Behnke’ was found and named by Mr. Behnke’s grandson, John Peter Thompson. The best red we carry is ‘Fireball,’ which has much larger blooms than the popular ‘Lord Baltimore.’ Our best selection of hibiscus is from mid-June to mid-August.

Last year’s Perennial Plant Association Perennial of the Year was Nepeta faassenii ‘Walker’s Low,’ one of a number of blue-flowered catmints. They begin to flower in late May or early June, and will continue through the Summer. Bees are fond of the flowers, and it being a close cousin to catnip, you may find that cats are romping in the garden as well. Nepeta subsessilis and Nepeta x ‘Joanna Reed’ have darker blue flowers than the others.

Perovskia, Russian sage, begins to bloom in late June and continues to bloom into September. The foliage has a strong medicinal smell when crushed. There are several cultivars with subtle differences; all have pale blue flowers; ‘Little Spire’ is shorter with stronger stems than the others. They are quite reliable and always look great with Echinacea.

Joe Pye Weed is a real butterfly magnet. Although some of the eupatoriums are too weedy for all but the most informal garden (spreading by seed or runners) there are three that will perform well in most garden situations; all are smaller than the species and all have dusky-rose colored clusters of flowers. The industry standard is Eupatorium maculatum ‘Gateway,’ which gets six feet or more tall. A more recent introduction is E. dubium ‘Little Joe,’ which is said to be three to four feet but seems to be four feet plus here in our warmer climate. A new one for us last year is the hybrid, Eupatorium x ‘Phantom,’ which is supposed to finish out at two to three feet. Flowering begins in July and runs into September.

So: some take home messages; enjoy your Summer garden; extend your blooming season with judicious use of shears and pruners; stop by every few weeks to see what is in bloom; and, plant natives as the backbone of the garden, accenting with carefully chosen non-native plants.

* Further information on this in Tracy DiSabato-Aust’s book, The Well-Tended Perennial Garden: Planting and Pruning Techniques, a must for all gardeners.

by Larry Hurley, Perennial Specialist

Larry Hurley

Larry Hurley, perennials specialist for Behnke Nurseries (now retired), started with Behnke’s in1984. Larry enjoys travel, food and photography. He and his wife Carolyn have visited Australia, New Zealand, Thailand, Brazil, South Korea and much of Europe. Their home is on a shady lot where a lot of perennials have met their Maker over the years.

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