Life After Labor Day
In late August, September and October, there isn’t a lot happening in most perennial borders. Even the long bloomers, such as coreopsis, are winding down. While the spring flowers slide into their time of rest and relaxation, the challenge for many of your customers is to get out of the mum mold – to find a few plants that don’t look like the expected. There’s a market for the unconventional, and you can take advantage of it by offering more fall perennials than just Sedum ‘Autumn Joy’. There are a number of attractive, late-blooming plants you can offer, and with proper marketing, well-organized displays and knowledgable staff to support them, you needn’t despair – there is indeed “Life after Labor Day.”
The following species have all performed well in the demonstration gardens at Michigan State University (MSU). Among other things, we are trying some less-common species of aster, moving away from the rust-prone types that we have grown in the past. Some of these plants have been featured in previous GPN articles on the perennial trials at Michigan State; these plants, as well as a few bulbs, have really impressed me with their long bloom period, and they deserve inclusion as components of a fall planting. Many late-blooming native plants have also been selected and bred for superior flower and leaf color and production. Finally, while I will not emphasize them in this article, tender perennials, such as cannas and dahlias (particularly those with colored foliage), are wonderful, easy-care workhorses in any border and do a good job of bridging flowering gaps during the season.
This plant’s shrubby habit gives it a nice presence in the border even when not in bloom. The foliage is fine-textured, a deep green color touched with purple. In cultivars such as ‘Lady in Black’, breeders have produced a plant with deep coloration. This sets off the thousands of tiny, white, starry flowers that blanket the plant. The petals have faint purple tips with centers that are yellow to pink in color. Our plants are next to a group of Sedum ‘Autumn Joy’ – the bold foliage and flower clusters of the sedum next to the aster’s fine texture make a nice pairing and would create an effective display combination in your store. A. lateriflorus is a native plant and has not been troubled by any foliar diseases or insect pests.
Aster tataricus ‘Jin Dai’
This aster is native to Siberia, giving it a good hardiness rating. It is a large plant, up to six feet tall, with large leaves. The foliage is unlike that of many asters, as it consists mainly of a rosette of large, basal leaves (Allan Armitage has likened them to Swiss chard). In Michigan, the plant blooms in late September and October. The flowers are a very attractive, medium purple with bright gold centers. Jin Dai, at 3-5 feet, is shorter than the straight species, making it a bit easier to use in the border. The one drawback we’ve found with this plant is that meadow voles find the roots delicious.
Aster laevis ‘Bluebird’
Smooth aster is a native species that seems remarkably disease free in our garden. The performance of this aster was good for the first two years, but when it bloomed in its third year, Bluebird stopped visitors in their tracks. So many flowers were produced that no foliage was visible, and the display was effective for three weeks. We have found that rabbits like this species, so we cage the plants. The leaves, as implied by the name, are not hairy, and are a fine, deep green. Garden designer Laura Coit reports that Bluebird is far superior to the straight species, even in cultivation.
This tough bulb not only blooms in the fall, but is also unattractive to deer and rodents because it is poisonous. The large bulbs increase gratifyingly in a location where they are happy. They produce a lush crop of large, ribbed leaves early in the spring, which wither and disappear in the summer. Then in the fall, the plant produces a cluster of pink, goblet-shaped flowers. More flowers appear for 1-2 weeks, so the display usually lasts for 2-3 weeks. It is particularly effective when paired with Scabiosa ‘Pink Mist’, as the two shades of pink form a very satisfying color echo.
Eupatorium coelestinum / Conoclinum coelestinum
Hardy ageratum is the common name for this species, and that is exactly what it resembles. The habit is taller than that of most annual ageratums, but you can prune the plant early in the summer to produce branching; left unpinched, plant height is approximately 24 inches. This species should probably be considered a ground cover, as it is rhizomatous and will wander through the garden. This habit can actually produce some serendipitous associations that turn out to be very attractive – one of our plants stealthily inserted itself into a nearby edging of sweet alyssum, a combination that is much nicer than either alone. Eupatorium coelestinum is a native plant, untroubled by pests. It is available in violet and white.
Eupatorium rugosum ‘Chocolate’
Another eupatorium that has been improved through breeding is Eupatorium rugosum. The cultivar Chocolate, a selection of the older ‘Braunlaub’, has deep, bronzy-green leaves that pair well with other plants, making it a valuable contrast plant in the border. It has not proven to be totally hardy in Michigan and is probably best considered a zone 6 plant. I had it planted next to Gaura ‘Siskiyou Pink’ whose pink flowers, combined with the bronze foliage and white flowers of the eupatorium, made an outstanding association. It has also proven to be an excellent container plant. A short-day plant, Chocolate is in its glory after Labor Day; a mature plant in bloom is absolutely drenched in flowers.
This erigeron was a test item in the MSU Perennial Trials for three years and performed admirably, blooming all summer until frost. In our 2000 trials, the first flowers were produced May 31, and the plant was still in bloom October 4. The plant’s habit is mounding, and the flowers, borne in loose clusters, are a rich violet with gold centers. It is not palatable to Japanese Beetles, though it does seem to get some light flecking each year from an unseen insect pest on the foliage. Plants expand to form a large continuous group but do not self-seed or spread by rhizomes. This is a great alternative to asters when customers are looking for summer through fall performance.
Though not a long-lived perennial (some classify it as a biennial), this plant has been overlooked for too long. Until recently, it was difficult to find it commercially, but when the Georgia Gold Medal for Outstanding Garden Merit accorded it some long-overdue recognition in 1996, the picture changed for this native of the central and southeastern United States. The first difference you’ll notice are the lobed lower leaves (hence the name ‘triloba’). The flower stalk is also highly branched, giving the whole plant a much airier look than many coneflowers. The flowers are far smaller than other species, with appealing little petals and a chubby, chocolate-purple eye. I find them to be nice cut flowers as well; they look particularly good with purple New England Asters, as well as solidago, and are a knockout with spires of Verbena bonariensis punctuating the display.
Rudbeckia nitida ‘Herbstonne’
At 5-7 feet, this is not a plant for the faint of heart. However, in a large border, it makes a spectacular anchor. The exact species of this cultivar is subject to debate; Allan Armitage reports that it is probably a hybrid between R. laciniata and R. nitida. It is a sturdy plant despite its height: In the face of our often violent thunderstorms, it remains upright and strong. The flowers, a clear lemon yellow with a prominent green cone, are large and borne over an exceptionally long bloom period. Stretching until well after Labor Day, this lofty flower display helps fill the border. No major insect pests seem to bother it. Rabbits are interested in the young plants, so some protection may be useful in the spring.
This plant is one of the longest-blooming perennials in our display garden. The display starts in July and goes until very hard frosts. Deadheading may increase the number of flowers, but the display continues whether or not the blooms are removed. One of my favorite associations in the garden is Autumn Crocus Colchicum autumnale and this plant. The color echo is lovely, and the show continues for several weeks.
Solidago rugosa ‘Fireworks’
I wish U.S. gardeners enjoyed goldenrod more. I am sure the aversion stems from deeply ingrained beliefs that goldenrod causes hay fever (I even had a physician ask me about this once; he had always thought goldenrod was allergenic). However, with the breeding work being done in Europe, much better varieties have been developed. One such selection is Solidago rugosa ‘Fireworks’. This plant has spectacularly long-arched flower plumes that remind one of exploding fireworks. While it does travel a bit, it is much better behaved than its rampaging cousin. The graceful gold flowers look very nice with ornamental grasses and red sedums. No pests or diseases have affected it.
This is another trial perennial that I have become very enthusiastic about, though its test period has not yet ended. Geranium Rozanne has an extraordinarily long blooming period. Most hardy geraniums have a magnificent but brief bloom period and often look a bit shabby afterward. Not Rozanne. The foliage received very high marks for quality after the plant was established, and the plant formed large, lush mounds while it threw out wave after wave of flowers. Rozanne was developed as a cross between G. himalayense and G. wallichianum ‘Buxton’s Variety’. The flower is blue-violet with a white eye. Last year, it was in bloom from June 7 until October 4. The developer, Blooms of Bressingham N.A., reports that it has also performed well as a hanging basket plant. This should be a valuable addition to borders at least to zone 6 and perhaps to zone 5.
So there you have them, a dozen great alternatives to the usual fall perennials that will carry the show in your customers’ borders well past the “August doldrums” and Labor Day. When complimented with annuals and tender perennials such as cannas and dahlias, there’s no reason a border can’t shine until October.