Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
"The sweetness of summer...becomes more concentrated toward the end. That wish of childhood, the longing to hold back the season, revives again." —JOURNEY THROUGH SUMMER, EDWIN WAY TEALE
Article by Bibi Wein · Photography by Bob Fisher
TWO SUMMERS AGO, as I followed the progress of my plants through spring to early August, I saw climate change writ large. Perhaps you've had a comparable experience. Where I garden, 250 miles north of Manhattan, we had record heat that May. We were planting on a date when, half a dozen years ago, we'd have been celebrating the first patches of bare ground, while winter's snowdrifts hung on like granite. June brought frost that stunted the tomatoes but did nothing to slow down the flowers. Lilies were early and fleeting. Phlox and monardas, once robust into September, were fading by August 10, when purple coneflower, one of our latest bloomers, was in full flower.
Along the rural roadside, milkweed was already reduced to pods bursting with soft white filaments and black seed. It was too bad for the monarch butterflies seeking sustenance for their long migration — and disappointing for gardeners facing the last precious weeks of summer asking where all the flowers had gone.
Although flowers seemed to be blooming and fading like a tape run too fast, we gardeners had logged as many hours, gotten just as dirty and endured as many bug bites as we have in more rewarding seasons. With all that work, how much more could it take to count on flowers through Labor Day? Very little, I soon learned. And nothing that involves tinkering with processes best left alone. You can enjoy fresh color and delightful fragrance in your garden through August, September, October and beyond, by doing three things as ecologically sound as composting potato peels. Plant late-blooming native perennials, deadhead throughout the summer and schedule some carefully timed pruning.
PLANT RELIABLE LATE BLOOMERS
There are no immutable rules about when and how long plants will flower, because no growing season mirrors another. Species of most of the genera discussed below are native in much of North America and, barring unforeseen weather conditions, will flower until first frost or beyond. Asters (Symphyotrichum spp. and related genera), in white through shades of purple and blue, and contrasting goldenrods (Solidago spp.), in sunny yellow, are not only easy to grow but important for the environment. "Their leaves are food for about 100 species of caterpillars, along with many other leaf-eating insects. The flowers provide pollen and nectar in abundance, and the seeds are eaten by birds such as goldfinches, towhees, white-throated sparrows and chickadees," says William Cullina, executive director of the Coastal Maine Botanical Gardens. Other members of the Asteraceae such as the Joe-Pye weeds (Eupatoriadelphus spp.), ironweeds (Vernonia spp.) and sunflowers (Helianthus spp.) come in a close second. Cullina likes to combine tall vernonias with flat-topped white aster (Doellingeria umbellata).
All of the eupatoriums, which include the dusky rose-colored Joe-Pye weeds and white boneset have numerous fuzzy flowerheads, large or small, in rounded or flattopped clusters. Mix eupatoriums with equally fuzzy goldenrods and deliciously fragrant steeplebush and meadowsweet for a soft-hued, impressionistic effect. Contrast, if you like, with the strong flower shapes and bright colors of monardas and echinaceas.
SOME GREAT LATE BLOOMERS, including false dragonhead and some of the asters and goldenrods, can reproduce so prolifically they seem bent on taking over the entire garden. Here's some expert advice on how to keep them in their place.
Most of these feisty species spread through runners. "If you know the plant tends to spread, plan for it," advises William Cullina, author of "Growing and Propagating Wildflowers," who likes to take advantage of a species' spreading habit by massing in a large area. "If it gets out of hand, edit back." He does this with an energetic plunge of a sharp spade. Repeat until you've outlined the allotted space. "You should only have to head them back once a year," he says. For almost surefire control, fill in the outline you've made with a barrier of 12" or more of roof flashing or other steel edging material, suggests Andrea DeLong-Amaya. She also likes to contain potential troublemakers in pots, tubs or planter boxes. "But aggressive plants may escape out of holes in the bottom," she warns. "Put the container on a patio – or keep an eye on it."
For better or worse, some species should be avoided unless you are revegetating or naturalizing a large area. Both Cullina and DeLong-Amaya find Canada goldenrod too aggressive, and Cullina adds that there's some research that this species releases chemicals that subdue other plants. Common species that can overrun Southwestern gardens include the ruellias, otherwise known as wild petunias. "I wouldn't discourage people from using them outright," says DeLong-Amaya, "but use them where you don't mind them spreading. Avoid non-native Mexican petunias (Ruellia brittoniana) in a garden setting. And be careful with rock rose pavonia and giant spiderwort. Some people find them too prolific. You can experiment but not long enough to let the species eat your yard. When you're planning your garden, find out which plants are rhizomatous or heavy seeders and avoid them, or use them with the greatest caution."
Many of these adaptable, problem-free plants will tolerate some shade. As Cullina points out, woodland sunflower (Helianthus divaricatus) is lovely along a driveway or at the edge of the woods. Pair up with shade-loving white snakeroot (Ageratina altissima) for contrast. Jerusalem artichoke (Helianthus tuberosus), though generally described as a sun-lover, has thrived in part shade in my garden. If your soil holds moisture well, try Canadian burnet (Sanguisorba canadensis), native to northeastern Canada and the United States south to Georgia, and to Oregon and Washington north to Alaska. It can stand an imposing 5 feet tall, and its breezecatching white fringe of blooms on a bottlebrush spike provide a strong vertical accent.
In my garden, false dragonhead, or obedient plant (Physostegia virginiana) thrives in sun or shade, poor soil or rich. It keeps up a show of stunning pink to white when the surrounding landscape is all fall colors and even the goldenrod is gone. The longlasting snapdragon-like blooms make great cut flowers. But beware — it can be robust enough to conquer all its neighbors. (See sidebar.)
Andrea DeLong-Amaya, director of horticulture for the Wildflower Center, points out that in hot, dry Texas and elsewhere in the Southwest, many spring bloomers go dormant through early summer, then bloom again in late summer through fall. "In Texas, these include cherry and mealy blue sage (Salvia greggii and S. farinacea)," she says. Texas lantana (Lantana urticoides), purple coneflower (Echinacea purpurea) and Zexmenia (Wedelia texana) do the same.
For a focal point in the Southwestern garden any time of year, nothing can beat the power and drama of a century plant (Agave americana). Despite the myth that gave it its name, century plant doesn't take 100 years to bloom, though it may take 10 or more. What triggers its bloom is not well understood. It's very drought-tolerant, as are the border plants DeLong-Amaya recommends, including blackfoot daisies (Melampodium leucanthum), rock rose pavonias (Pavonia lasiopetala), globe mallows (Sphaeralcea spp.) and liatris (Liatris spp.).
For color contrast, perennials in shades of true red through vermilion and orange offer numerous options for eye-popping brilliance. Cardinal catchfly (Silene laciniata) and mountain sage (Salvia regla) are just two of many choices.
Showy reds with a larger native range include zippy red and yellow blanket flower (Gaillardia pulchella) and bold crimson cardinal flower (Lobelia cardinalis), which dazzles from a much greater distance than its relatively small size and delicate form would suggest. If blue is your passion, less common but worth tracking down for their unique colors and forms are the eryngiums, with silvery purplish bracts that remain eye-catching long after the thistle-like blue flowers have faded, and the more diminutive blue bottle gentian (Gentiana andrewsii or G. clausa). Consider them, or any of the native blue perennial sages, alongside orange butterflyweed (Asclepias tuberosa) for stunning contrast.
Many perennials we think of as summer flowers can be carried well into autumn if the spent flowerheads are pinched or sheared back to the next set of leaves before they set seed. It may seem tedious, but make deadheading a habit and some mints, with their small but lovely blue-violet flowers, most sages, achilleas and phlox can make a repeat appearance late in the season. This simple technique also will extend the flowering season of many other perennials including asters, goldenrods, blanket flower and red gilia. For small flowers that grow in spikes — like the cardinal flower — cut off the whole spike when most blooms are spent. If the stem is leafless, cut it down to the ground.
Where hot, dry summers mean more dormancy than bloom, deadheading can be less important. DeLong-Amaya points out, "You can deadhead mealy blue sage and it will push out continuously throughout the summer. But if you don't, it will produce more blooms in fall anyway."
Many late-blooming natives are large prairie plants, like Joe-Pye weed (Eupatoriadelphus spp.) and ironweed (Vernonia baldwinii), both of which may exceed 5 feet in height. You can keep them at a more manageable size by hard pruning early in the season. They will flower at their usual time or perhaps a bit later. Cullina advises, "If you prune back a plant to onehalf to one-third of its size around or before July 4, it won't necessarily flower later than usual, but they'll be shorter and bushier. Don't do this much later or it could interfere with flowering."
In her book "Late Summer Flowers," British botanist Marina Christopher suggests extending bloom by treating various parts of the border in slightly different ways. "For instance, a well-established patch of Phlox paniculata could be pruned more extensively at the front of the patch, more lightly in the middle, and least if at all at the back." Flowers would appear in backto- front succession, after which they can be deadheaded to start all over again.
Cullina has one serious rule to add for gardeners in his Northeastern region: "Be careful using fertilizer and pruning after August." These can stress many plants at this point in their cycle by causing late season growth that is subject to winter damage. For most plants, apart from deadheading if you wish, it's time to let nature take her course.
To lift the spirits as the season ebbs, there's nothing like a profusion of flowers backed by the low sunlight of late summer and autumn. And the nectar they provide for hummingbirds, bees and butterflies comes at the most crucial time in their cycles. If you enjoy not only the visual and olfactory delights of your summer garden but the hum and buzz as well, planning and planting for a long season will keep the music flowing well into fall.
Bibi Wein is the author of "The Way Home: A Wilderness Odyssey" (Tupelo Press), an environmental memoir about the Adirondacks.