Crowd-pleasing Plants at Coastal Maine Botanical Gardens

Text by William Cullina, President & CEO of Coastal Maine Botanical Gardens, for Horticulture’s February 2013 issue.

One challenge all public gardens face is keeping floral displays novel and colorful throughout the seasons. At Coastal Maine Botanical Gardens we design gardens with a range of plants that bloom over a long season, so there will be crowd-pleasing color whenever folks visit. Here are nine visitors’ favorites, one from each month of our March to November growing season.

March: witch hazels
March in Maine can be mild one week and icy the next, and most plants remain dormant. However, a few stalwarts risk their delicate flowers at this most indelicate time of year. Perhaps the most notable of these are the witch hazels, large shrubs or small trees from eastern Asia and the United States that produce thin, warm-hued blossoms of remarkable resiliency. For general garden use, the best of the lot are the hybrids between the Japanese and Chinese species, called the Hamamelis ×intermedia group. Among the many excellent cultivars on the market, a staff and visitor favorite here is ‘Pallida’, a bright yellow, extremely fragrant selection that will bloom reliably in partial sun to light shade and fertile soil. It is hardy in USDA Zones 5 through 8.

April: hellebores
Toward the end of March and on through much of April, hellebores awake from their light and restless sleep and begin to stretch toward the warming sun. If you have grown hellebores in colder climates, it will come as no surprise that the most long-lived and reliable crowd pleasers in our collection are the Helleborus orientalis hybrids (H. ×hybridus; Zones 4 (with snow cover)–9). Though it takes them a few years to settle in and grow to their full potential, these semi-evergreen to evergreen woodlanders produce bouquets of leathery, long-lasting flowers in just about every shade, save orange and true blue. I am partial to the double-flowered forms, as they have more visual presence than the nodding, single types. After a long winter, the large, fingered evergreen leaves look flattened and tattered, and I quickly remove the worst of these before the flower stalks begin to grow.

May: tulips
For sheer color and impact, it is hard to beat tulips. Like many, I have for years been laboring under the impression that tulips are perennials to be welcomed again and again during April and May. While they are truly perennial under optimal conditions, more often than not, competition, poor soil and hungry rodents lead to their premature demise. However, if you view tulips as a one-shot display planted in autumn, enjoyed in spring, then removed before summer to be replaced by more traditional annuals, they can be eminently satisfying. For the past few years we have been planting blends purchased from suppliers or mixed ourselves. Because the blends make use of common, less-expensive varieties, they are cheaper than fancier types; you can order them by the hundred or thousand for as little as 25 cents per bulb.

June: peonies
Each year our collection expands, and each June my passion increases for the Itoh peonies, which offer the vigor and heavy flowering of the herbaceous types and the large flowers, strong stems and lovely foliage of the tree species. Of the many we grow, the true standout with our guests is Paeonia ‘Bartzella’ (Zones 4–8), a three-foot-high plant that covers itself in six-inch-wide, translucent yellow flowers stained red at their core. It is so spectacular in flower that it draws the eye from a hundred feet away, and the blooms keep coming for several weeks once the plant is fully mature. Though they are pricy, Itoh peonies are very long-lived and problem free in full to partial sun and moist soils. Because it takes three to four years for them to fully mature, it is worth spending a few extra dollars to start with a large, well-rooted specimen.

July: roses
Late June into July is when roses come into peak bloom in our neck of the woods. A new generation of lower-maintenance garden roses has breathed new life into what was a rather old-fashioned genus on the wane in gardens. One that I feel deserves mention is Macy’s Pride (‘BAIcream’), a pale yellow to ivory, disease-resistant shrub rose from renowned breeder Ping Lim. It is part of Bailey Nurseries’ Easy Elegance line. The flowers are large and strongly fragrant. The four-inch blooms come in a flush in late June then appear sporadically through the season. The plants in my own garden keep producing the odd flower until nearly Thanksgiving if mild weather prevails.

August: coneflowers
During my time in North Carolina in the mid 1990s, I was involved in the introduction of ‘Kim’s Knee High’ purple coneflower—one of the first of what is now a very long list of coneflower selections. In the last 10 years the trickle of new hybrids has turned into a torrent. There are double and semi-double, tall and short varieties, and it is too soon to tell which of these legions will stand the test of time. Though my own taste trends toward the wild coneflowers, ‘Hot Papaya’ (Zones 3–9), a blood-red double that fades to orange as it ages, elicited the most comments from our guests when it was blooming in late July through August. Grow it in moderately fertile, well-drained soil and full sun.

September: swamp mallow
Every year just after Labor Day, pure white flowers the size of dinner plates appear to the delight of late-season guests: flowers of the swamp mallow Hibiscus moscheutos ‘Blue River II’ (Zones 4–9). They are huge but not gaudy, and the five-foot-high perennial remains in bloom through most of September. Swamp mallow begins growing late in the spring, sprouting stout stems clothed in large oval leaves from a mass of fleshy roots that relish—but don’t require—mucky soils. We grow them in moist soil and full sun, and the clumps become almost shrub-like by late summer when the flowers appear from the stem tips.

October: Japanese stewartia
There are many shrubs and trees that deserve mention for their fall color, but I have room for only one, so I will pick the Japanese stewartia (Stewartia pseudocamellia; Zones 5–8). A slow-growing tree with white summer flowers the size of silver dollars, Japanese stewartia smolders rich scarlet in leaf for several weeks during pumpkin season. The leathery leaves are slow to turn and slower to drop, but when they do they reveal smooth, patterned bark in shades of pink, olive and tan. Because of its beauty and long season of interest, Japanese stewartia is a popular specimen for the smaller property. Be advised, though, that with time it will grow to 40 feet or more, so locate it away from structures and power lines. It thrives in moist, well-drained soils and full to partial sun.

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