Plants for the Cold

Credit: John Glover/DavidTarrant/Al Dodson/Bob Gibbons/Rosie Mayer/Patricia Habidgell

These sturdy choices withstand winter’s chill and are ideal for B.C.’s northern gardens

Those of us in the mild southwestern corner of B.C. often forget about the challenges faced by our fellow gardeners in the colder parts of our province. Over the years I have had the pleasure of seeing gardens in some quite remote and beautiful areas, such as the town of Atlin in its magnificent setting on the lake surrounded by spectacular mountains. Another lovely spot is the community of Dawson Creek, way up in the Peace region close to the Alberta border, with its heritage gardens that welcome summer tourists as they make their way to the Alaska Highway. There are many attractive plants hardy to such areas, and this seems like a good time of year to highlight some as you sit in the cozy warmth of your home, dreaming about next season’s garden.

Attractive, cold-hardy plants

Acer tataricum ssp. ginnala, more commonly known as Amur maple, is a very nice-looking small tree or shrub native to northern China and Mongolia, making it hardy to zone 2. This delightful shrub can be up to 5 m (16 ft.) tall. Its leaves are opposite and about 7 to 10 cm (2.8 to 4 in.) in length. An elongated central lobe and two smaller ones on each side give them a maple shape. The veins on the undersides of the leaves and the petioles are deep red, adding further interest to the plant. In spring the stems bear tiny panicles of scented yellowish-white flowers. In fall the foliage turns a glowing orange red. But buyer beware – the colour varies from specimen to specimen according to Sara Williams and Hugh Skinner (authors of Best Trees and Shrubs for the Prairies, published by Fifth House in 2004). It’s best to purchase these trees in fall as container plants, when their true colours are showing. I prefer them left as multi-stemmed specimens, which I think gives them a bold presence in your garden. A grouping of three would be even more impressive in fall. However, some people like to keep them pruned to a single trunk, reminiscent of Japanese maples, which are only hardy in the south. I once saw one pruned in such a manner, with its trunk slightly angled out over a small pond next to a stone lantern. The whole scene was quite exquisite and brought a touch of Japan to a northern garden. Aesculus glabra, or Ohio buckeye, is another good choice. It is, in fact, native to central and eastern zones of the US and is hardy to zone 3 and up. This delightful tree grows to 15 m (50 ft.) in height and is under-used in colder gardens. The form of the tree is broadly conical – somewhat like the outline of a tree one drew as a child. The foliage is typical of a horse chestnut, palmate with five leaflets, each ovate, pointed and up to 15 cm (6 in.) in length. In fall they turn a beautiful warm yellow. The small, creamy-white flowers are clustered into an upright, cone-shaped inflorescence that reaches 15 cm (6 in.) in length and develops into very sparse prickly fruits. One caution here: all parts of this tree, including the fruits, are poisonous. Bergenia cordifolia is well known to gardeners throughout the temperate world. Native to Siberia, it can tolerate zone 3 and warmer. A clump-forming evergreen perennial, its rounded, leathery leaves are up to 30 cm (12 in.) long. In summer they are a glossy green but become tinged attractively red during winter. The thick, almost succulent leaves persist under snow, and welcome the sun as the snow melts above them. Then the plant sends up 30- to 60-cm (1- to 2-ft.) red stems carrying clusters of dark-pink flowers. Bergenias withstand extremely cold temperatures yet have an astounding tolerance of summer drought. They certainly don’t seem to be fussy about soil types. In the exquisite Japanese Garden at the University of Alberta Devonian Botanic Garden are mass plantings of bergenia among rocks. The sight of this in bloom – creating a 2-m (6-ft.) wide burst of pink blossoms in a northern spring certainly lifts one’s spirits. Clematis tangutica, the famous “lemon peel” clematis, is incredibly hardy. I well remember seeing it flourishing and full of bloom on the west wall of a house in Whitehorse. It comes from western China and is hardy to zone 2 and up. This is a vigorous climber or sprawler (it looks nice either way). The flowers appear later in the season and are abundantly borne on solitary stems in a Chinese-lantern shape 4 cm (1.5 in.) long. The bright lemon-yellow petals are thick and leathery to the touch. As the flowers fade they produce fluffy seed heads that stay on all winter long. It looks great on a trellis but can look even more attractive if allowed to climb up through the lacy branches of a weeping caragana. In some places this clematis can be a bit invasive – in Alberta it is quite widely distributed on the banks of the North Saskatchewan River – so keep it in check and pull up any unwanted seedlings. Delphinium hybrids seem to love colder climates. I was absolutely taken by the fact that they happily seed themselves about and flourish in the ditches of Dawson, the home of the gold rush in the Yukon. There are, of course, many hybrids of delphinium on the market under such cultivar names as ‘Blue Bees,’ a superb pale baby blue, or ‘Blue Nile,’ which has deep sky-blue flowers with tiny white centres. They have typical deeply lobed buttercup-like foliage and flower spikes up to 2 m (6 ft.) in height. There are two factors for happy delphiniums: rich soil and guaranteed snow cover. This explains why they do so well in the ditches up north. So add plenty of compost at planting time, then top-dress with a 10-cm (4-in.) layer of compost every spring. Most winters up north get good snow cover, but with weather being so unpredictable everywhere these days, it is best to be prepared and cover clumps of delphiniums with chicken wire, twigs and leaves. Of course, you must wait until after the first couple of frosts before doing this, otherwise every little mouse and vole will be in there for the winter, feeding on the plants you are trying to protect.It’s difficult to track the origins of delphinium hybrids to determine their hardiness, but there’s one superb shorter-growing delphinium that I would recommend. Delphinium grandiflorum ‘Blue Butterfly’ is only 20 to 50 cm (8 to 20 in.) in height, with large single bright-blue flowers produced in open panicles. It is a short-lived perennial with parents from Siberia, so it’s hardy to zone 3. Hydrangea arborescens (sometimes called “hills of snow”) is indeed the truly hardy hydrangea. It mimics the growth habit of H. macrophylla (mophead hydrangea) but only produces white flowers. H. arborescens is native to the eastern US and hardy to zone 4 and up (although I have seen it growing in zone 3 in an area with good snow cover). It is a rounded deciduous shrub with ovate dark-green leaves that are darker green above and lighter on the underside. The flowers grow in corymbs, which at maturity can measure 15 cm (6 in.) across. They start out a beautiful green and open to pure white. The beauty of this species is that it blooms on the current season’s growth. There is a named form, H. arborescens ‘Annabelle,’ which has considerably larger flower heads – 30 cm (12 in.) across – and while it is extremely showy, the heavy blooms tend to weigh down the branches. Lonicera x brownii ‘Dropmore Scarlet’ is another must-have vine for cold areas. It is one of the many plants in Canadian horticulture introduced from Agriculture Canada Research Station in Morden, Manitoba, and is hardy to zone 2. It has typical honeysuckle form with paired bluish-green leaves that are deciduous up north. The scarlet flowers, each individual flower 4 cm (1.5 in.) in length, are borne in terminal whorls. If the season is long enough, they have bright red berries in late summer. The showy flowers have a long bloom time and, of course, attract hummingbirds. I saw a most innovative planting of this vine in Alberta: a bamboo trellis was placed close to a kitchen window so the hummingbirds were nearby and right at eye level. Nepeta sibirica is an invaluable hardy perennial and sadly underused. As the name suggests it is native to Siberia, and it is hardy to zone 3. It has an erect growth habit and branching stems with aromatic, toothed, dark-green leaves 9 cm (3.5 in.) in length. In midsummer it bears long and showy blue to lavender-blue flowers in whorls, and they last for quite a few weeks. If I gardened in the north I would have two or three clumps of Nepeta sibirica growing among two or three bushes of Rosa ‘Morden Blush,’ my favourite of all the roses developed in this country. It is shrubby, with floribunda heads of pale-pink roses shaped like many of the David Austin roses, and it’s hardy to zone 3. To keep both these plants happy, top-dress each spring with a 10-cm (4-in.) layer of compost or well-rotted manure. Last but not least, nine bark (Physocarpus opulifolius ), is a great shrub that can be used among perennials or in a darker corner of the garden. Native to eastern North America, it’s hardy to zone 3. My favourite form is P. opulifolius ‘Dart’s Gold.’ In ideal growing conditions this plant can be 2 m (6 ft.) tall and about 2.5 m (over 8 ft.) wide. The broadly three-lobed leaves are 8 cm (3 in.) in length and bright golden when young, maturing to a rather nice chartreuse shade. Corymbs of tiny, almost insignificant blooms are followed by bright red berries. It truly is a stunning shrub that adds life to a garden on a dull day. This colourful group of plants represents just a tip of the iceberg of truly hardy choices for colder climates. Hopefully, it will inspire all to seek out the many more plants available that are perfectly at home in the beautiful northern reaches of our province. Further reading on hardy trees and shrubs: Best Trees and Shrubs for the Prairies, by Hugh Skinner and Sara Williams. Published by Fifth House, ISBN 1-894004-95-7. The following plants are hardy to the zone number indicated: • Acer tataricum ssp. ginnala – zone 2 • Aesculus glabra – zone 3 • Bergenia cordifolia – zone 3 • Clematis tangutica – zone 2 • Delphinium ‘Blue Butterfly’ – zone 3 • Hydrangea arborescens – zone 4 • Lonicera x brownii ‘Dropmore Scarlet’ – zone 2 • Nepeta sibirica – zone 3 • Rosa ‘Morden Blush’ – zone 3 • Physocarpus opulifolius – zone 3 David Tarrant of the UBC Botanical Garden is a well-known gardening expert, author, and host of Spring, currently on HGTV.