Tuesday’s Terrace: Autumn Cheer from Firethorn, Philadelphia, PA

unnamedInfrequently seen in gardens due to its fire blight susceptibility, Pyracantha (firethorn) here has been meticulously trained as an espalier over the front entry of a Society Hill home in Philadelphia. Its orange berries add a festive autumnal touch especially when Halloween is around the corner. The mums, while colorful, seem to be an afterthought in the glowing spectacle of the firethorn. ~ Eric

Anatomy of a Garden: Two Plantings at Lurie Garden

The principal genius of the Lurie Garden, conceived by Kathryn Gustafson, Shannon Nichol, Jennifer Guthrie (Gustafson Nichol Guthrie firm), and Piet Oudolf, lies in the ingenuity with which North American prairie plants are mixed with exotics to spectacular effect in an urban environment. A 15 ft tall hedge, a physical manifestation of Carl Sandburg’s “City of Big Shoulders’, gives muscular heft and the maple allees (Acer x freemanii [Autumn Blaze] = ‘Jeffersred’ keeps the scale proportional and intermediate between the skyscrapers and the perennial plantings. Because Chicago’s cold and snowy winters can truncate the winter interest of herbaceous plantings that Piet Oudolf is famous for, the structural stillness of the hedge and maple trees cannot be underestimated and by its virtue of solid mass, the former makes the garden’s loose naturalism more marked during the growing season, and the latter intercepting light at a higher level. Had not the Gustafson Nichol Guthire firm and Oudolf been perceptive to create this framework, the Lurie Garden overall looks lost against the domineering Chicago skyline. Below are two photographs of different plantings taken at different seasons.

One could say that the first photograph of the garden in autumn resembles abstract expressionism since colors – the scarlet ridge of maples, the angular contours of the hedge, the tawny seedheads of Panicum virgatum ‘Shenandoah’, and the fine loose foliage of Amsonia hubrichtii –  are sharply demarcated.

Amsonia hubrechtii in fall

 

1. Amsonia hubrichtii 

Restricted to the Ouachita mountains in Arkansas and Oklahoma, Amsonia hubrichtii commemorates the American conchologist (someone who studies molluscs) Leslie Hubricht who found it in 1942. Young plants resemble straggly pine seedlings, but will mature to form billows of fine-textured stems with 3 to 4 feet spread. Like other amsonias, Amsonia hubrichtii produces light cornflower blue flowers in spring. Although some garden writers have derided its widespread availability and potential overuse in landscapes, it still remains somewhat uncommon and should not be overlooked especially for its bright yellow autumn foliage. Full sun and regular soil will be satisfactory and a bit of self-seeding may be observed. The second photograph shows Amsonia hubrichtii in its spring attire (Number 6).

2. Panicum virgatum ‘Shenandoah’ 

One of the earliest switchgrasses to be introduced to the trade for its reddish foliage, ‘Shenandoah’ is a German selection by Hans Simon who evaluated more than several hundred seedlings of ‘Hanse Herms’. Leaves emerge green in early summer and develop reddish tints in midsummer. ‘Shenandoah’ does not flop and remains remarkably upright throughout the season. The downsides is that the foliage seems more susceptible to rust than the green or blue-leafed cultivars and the roots, aromatic when dug, are irresistible to rodents, especially voles.

3. Thujas (Thuja occidentalis ‘Brabant’, T. occidentalis ‘Nigra’, T. occidentalis ‘Pyramidalis’, and T. occidentalis ‘Wintergreen’, Thuja ‘Spring Grove’)

Different Thuja cultivars fill out the hedging that surrounded the perimeter of the Lurie Garden and diminishes the unsightly effect of winter damage were one variety used. In a heavily trafficked urban environment, the thujas do not suffer from deer depredation and remain evergreen.

4. Acer x freemanii [Autumn Blaze] = ‘Jeffersred’ 

Freeman maples are hybrids between Acer rubrum and A. saccharinum that combine the best attributes of their parents. The form and brilliant scarlet foliage is inherited from Acer rubrum, with rapid growth and urban adaptability from A. saccharinum. In Manual of Landscape Plants (2009), Michael Dirr noted that Autumn Blaze has ‘rich green leaves with excellent orange-red fall color that persists later than many cultivars, dense oval-rounded head with ascending branch structure and central leader, rapid growth and Zone 5 hardiness, may be more drought tolerant than true Acer rubrum cultivars.” Indeed the scarlet color is a worthy ornamental characteristic of Autumn Blaze. Dirr does express caution over the overuse of Autumn Blaze in commercial landscapes.

 

By contrast, the second photograph taken in early summer depicts the Lurie Garden painterly in the Impressionist manner – the drifted plantings orient in unusual angles, the colors appearing brushstroke-like, and plants an essence of their selves. Not surprisingly, the Lurie Garden Design Narrative describes this section “bold, warm, dry and bright” and the its topography  “a contoured, controlled plane experienced by walking on its surface.” Early summer is a bounteous time for herbaceous perennials which respond well to longer day lengths and consistent warmth.

female-redwing-blackbird-late-spring

 

1. Monarda bradburiana 

Monarda cultivars from Europe have largely overshadowed the native species from which they were hybridized, and it’s a shame since the species seem to exhibit better mildew resistance and adaptability. Native to open dry woodlands in Southeast US and northwards to Iowa, the Eastern bee balm has attractive silver-green foliage and creamy pink tubular flowers. The calyces age attractively to a wine hue, an additional seasonal interest after the main floral display has finished. Here in the Lurie Garden, the wine calyces connect visually to the dark globes of Allium atropurpureum. Pollinators are usually drawn to its nectar-rich flowers, giving a strong case to cultivate Monarda bradburiana.

2. Allium atropurpureum

I first saw this allium at Nori and Sandra Pope’s late Hadspen Garden, Somerset, UK where the dark purple florets echoed the purplish-suffused blue foliage of Rosa glauca in the plum border. Used alone, Allium atropurpureum looks lost, receding in the background. However, its dark tone is a good chromatic foil for the purple Salvia river and Baptisia ‘Purple Smoke’. Some accounts have noted the short lifespan of Allium atropurpureum although excellent drainage may be the difference between success and failure. Topping up the bulbs annually will offset any gaps and maintain the display overall.

3. Amsonia ‘Blue Ice’ and Papaver orientale ‘Scarlet O’Hara’ 

Of unknown parentage (one parent is certainly Amsonia tabermontana), Amsonia ‘Blue Ice’ originated in the stock beds of White Flower Farm several years ago. It is a superb garden plant for its all around good looks – the buds are a winsome dark blue, habit is tidy and manageable, leaves dark green and lustrous (turning yellow in autumn), and pests seldom trouble ‘Blue Ice’.

The bright splash of red orange from Papaver orientale ‘Scarlet O’Hara’ prevents the planting from looking sedate, polite for a lack of better term. In a mixed planting like the Lurie Garden, Oriental poppies can be tricky to integrate because they left gaping holes during summer dormancy and resent crowding when foliage returns in late summer and autumn. In addition, it is easy to plant in the empty spaces vacated by dormant Oriental poppies.

4. Amsonia tabermontana var. salicifolia 

Taller (24-36″) than ‘Blue Ice’ (12-15″) and bearing lighter hued flowers, Amsonia tabermontana var. salicifolia was among the first amsonias to be cultivated and still remains a classic for the perennial border. The terminal clusters of light blue flowers appear in spring and become bean-like seed pods in late summer and autumn. Be mindful of its siting since transplanting established amsonias is not a feat for the weak-hearted as their taproots probe long and deep.

5. Baptisia ‘Purple Smoke’ 

Sometimes the best garden plants are happy accidents and ‘Purple Smoke’ was a chance seedling discovered by the late curator Rob Gardner in the trial beds of Baptisia minor and B. alba at the North Carolina Botanical Garden. Sultry smokiness essentially sums up the appealing trait of this hybrid – the stems emerge an inky gray color rare among herbaceous perennials, the flowers a soft violet the color of evening dusk, and the pea-like foliage unfazed by heat and humidity. Mature plants can reach 50″ tall. In this planting above, the soft violet flowers are a good transitional hue between the salvias and Allium atropurpureum. Young plants do not resemble much and require some time to reach their full potential.

6. Amsonia hubrichtii 

Winter Flowers: Daphne

Daphne odora f. alba

Daphne odora f. alba

As the Chinese New Year (Year of the Horse) approaches at the end of January, my thoughts turn to the traditional container plants, like Prunus mume and citrus, which herald this auspicious holiday. Where winters are mild, daphnes coincide with Chinese New Year when they perfume the garden courtyards. They are usually Daphne odora, a species with a long history of cultivation.

Dahlia odora 'Maejima'

Dahlia odora ‘Maejima’

The Chinese once valued Daphne odora as a pot plant for its fragrance as well as planting it in their gardens. In Garden Plants of China (1999), Peter Valder cites a story of a sleeping monk who dreamed of a memorable fragrance and upon waking, sought and found the source of the scent, a plant he named Shuixiang (Sleeping Scent). Like other garden plants, Daphne odora was probably introduced to Japan from China. Several variegated varieties, such as Daphne odora ‘Maejima’, are valued by the Japanese. Taking their cue from east Asia and certainly seduced by the daphne’s scent, the Victorians grew this species in the conservatories and hothouses in the 19th century.

The gawky habit of Daphne odora resists pruning since lateral growths are rarely produced unless drastically cut closer and on mature wood. Complicating matters is the production of flowers in terminal inflorescences. My inclination is to let the plant mature more and then re-evaluate pruning, and in the meantime, one has to overlook the sparse branching. Viruses do plague Daphne odora  – yellowing or dying foliage and stunted growth are telltale symptoms. Tissue culture has done much to reduce the incidence of viruses as older stock propagated by cuttings became contaminated over time.

The starry flowers are set in clusters like brooches against the wavy dark green foliage.

The starry flowers are set in clusters like brooches against the wavy dark green foliage.

Daphne bholua is a familiar, welcome sight in Europe and Australia during winter when its starry flowers purple in bud and pink-blushed fully open wafted its intoxicating fragrance. Pronounced ‘bo-lua’, bholua takes its origin from the Nepalese name bhulu-swa. It is found in forests between 7,000 and 11,000 ft (2000 to 3350 m) in mountainous regions of Nepal and Bhutan. Plants at lower elevations tend to be more evergreen than those higher above that are semi-evergreen to deciduous, and selections from the latter will be clearly harder. Sadly for those in colder climates, Daphne bholua is more tender than Daphne odora, requiring frost protection as young plants and preferring sheltered sites for success. Seed-grown plants are slow to flower, but grafted or tissue-cultured plants will flower young. The habit of D. bholua is taller and fuller than that of D. odora, therefore formative pruning is less of an issue. 

Both daphnes make excellent cut flowers that emanate their fragrance in a warm room. Inside their fragrance may be too overpowering for some noses, but they chase away the winter blues, reminding us that the cold months are not without its floral interests.

Daphne bholua

Daphne bholua

Winter Flowers: Mahonias

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December can be a bleak month for flowers unless you count the odd, brave snowdrop  or a precocious witch hazel. The last of autumn leaves have fallen, and the late-flowering asters have gone to seed. While it is true that the bright red hollies can wake up our gray senses, they lack the sensual power of flowers, a strong reason for the magic of gardening. Only do the days become perceptibly longer in late January can we anticipate winter flowers even if they lack the spring pyrotechnics. Often the wait is rewarding for winter flowers can be intensely scented.
Why do these plants expend energy flowering when odds are stacked against them? Winter flowers do not have to vie for pollinators as they would have if spring and summer were their seasons. They’re savvy to recognize that those warm winter spells will revive any hibernating insects needing sustenance for the next cold spell. I am always taken surprise at seeing bees and various members of Hymenoptera (bees) and Diptera (flies) at what seem paltry options in winter. Somehow the plants do succeed when mature, ripe fruit take the flowers’ place later.
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Before Christmas, I can always count mahonias to commence the winter flowering season. Their sprays of yellow flowers glow bright and incandescent in the weak winter light, luring us as much as those hapless pollinators. Sweet and heavy like honey, the mahonia’s perfume can cut through the chill like a scythe in a wheat field. It is faintly suggestive of lily of the valley, but more potent in its intensity. The best mahonia for fragrance remains Mahonia japonica, a species curiously not found in the wild.
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Lax and wide spreading in habit (6 ft tall by 5-7 ft wide), Mahonia japonica can be hard to accommodate in small gardens. And despite being highly scented, the flowers of M. japonica may lack the showiness factor people seek in winter flowering shrubs. Those willing to accept less fragrant, but showier flowers can look towards Mahonia x media.
A hybrid of M. oiwakensis subsp. lomariifolia (syn. M. lomariifolia) and M. japonica, Mahonia x media originated in the batch of open-pollinated seedlings in northern Ireland. One seedling was grown at Savill Gardens, England, where it was named ‘Charity’ (its siblings were respectively named ‘Hope’ and ‘Faith’). Breeders expanded the selections, which vary in flowering times and mature sizes. Generally Mahonia x media tend to form taller, if not tighter, statuesque shrubs than M. japonica. They are surprisingly architectural as their leaves have this precise zig-zag pattern somewhat tiered on the stems.
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Some people are highly dismissive of mahonias’ ranginess over time. Pruning the stems hard to 1′ to 2′ will encourage new shoots to develop – it is advisable to cut in spring for the plant to heal and regenerate rather than autumn or winter. Others might view the leggy stems as an opportunity to underplant with interesting shrubs or perennials to conceal them.
Mahonias do best in mild winter regions. They require protection from winter winds, which can scorch and tatter their beautiful foliage. Although the damage appears cosmetic, the effect is rather distracting for the evergreen leaves can be long-lived. In fact, open and sunny exposed locations are not ideal for mahonias, which tend to be understory shrubs in the wild. I often see robust plants in northern exposures, and in dry shade where other plants would fail. It is a common sight in London to see mahonias somehow flourishing in those dark corners, lurking furtively until their flowers appear, awakening the bleary landscape.