Shrubs are the backbones of the landscape. Their larger size gives the design a framework and imbues the area with life, particularly when their own flowers bring a particular “wow” factor to the rest of the plantings. Because shrubs are such an important aspect of your botanical storyboard, it’s a big disappointment when they don’t survive the winter. Choosing the right shrub for a harsh northern climate ensures beautiful blossoms even after brutal winters.
Perennials are typically chosen for their flowers, but shrubs often offer the best of both worlds, with interesting basic structure topped with gorgeous flowers in the spring and early summer. And, thankfully, there are a number of species and cultivars that thrive even in the harsh conditions of many northern climates. Choose wisely and plant a rugged spring- or summer-blooming shrub this fall, then look forward to the flowers without worrying about the plant.
Winter into Spring
There are few shrubs that provide such dramatic winter interest as redosier dogwood (Cornus sericea), with its bright red twigs standing out against the white landscape. They’re also a favorite because they thrive in sunny to partly shady locations, they aren’t picky about soil type and they tolerate wet soil as well as drought.
The cultivar ‘Cardinal’ (USDA Zones 3–8) is a longtime favorite. It can reach nine feet tall and it generally blooms between May and June. For a compact version that still has all of the great features, look for Kelsey’s dwarf (‘Kelseyi’; Zones 2–8). Even though it’s only three feet around, this is a tough plant that creates a beautiful form in the garden.
One trick to ensuring bright red stems is to cut the oldest stems to the ground every couple of years to promote new growth, which shows the most brilliant winter color.
Keep in mind that when choosing hardy shrubs, there are certain kinds that perform better in northern conditions. For example, forsythia (Forsythia), the cheery, yellow harbinger of spring, are indestructible in Zone 5, but they may not bloom as well in colder regions, where their buds, which are set in the prior growing season, may freeze. Thankfully, horticulturists have resolved that issue in a handful of cultivars.
The meadowlark is the state bird of Montana and the true sign of spring there. Its namesake forsythia lives up to its moniker. Hardy in Zones 3 through 8, ‘Meadowlark’ forsythia is a northern cultivar created to bloom even when the temperatures drop to -35˚ (F). This is a large shrub that grows up to nine feet tall and nearly as wide. It can grow a little leggy, but this is easily remedied by pruning the shrub after it flowers in the early spring. This is one of the toughest of the forsythia cultivars, reputed to live up to 40 years. Grow it in full to partial sun. One particularly nice feature about this cultivar is its tolerance of salt from roads or sidewalks; it can be planted where the melt from these areas seeps into the garden bed.
Blossoms and Berries
Called Juneberries in some regions, the serviceberry (Amelanchier) provides beautiful, fragrant, white blooms in March and April followed by a crop of berries for human or wildlife consumption. Many of the native versions grow as small trees unless pruned accordingly, but there are cultivars that maintain a more consistent form.
For a smaller option, consider the eastern native roundleaf serviceberry (A. sanguinea; Zones 3–6), which grows just six feet tall. This species has bright reddish foliage in the fall and red twigs throughout the winter.
In general, serviceberries are happy with sun to partial shade. They grow best in slightly acidic conditions and they don’t require an excessive amount of water. Consider putting them in an area where they can spread, because many have a tendency to do so. This is a benefit for naturalized areas, but it can be problematic in more formal plantings.
A Sweet Scent
Overall, mockorange (Philadelphus) shrubs are notably tough. The western native species Lewis’s mockorange (P. lewisii) was named for Meriwether Lewis by the botanist Frederick Pursh when he cataloged specimens the former collected in 1806. With pure white, large, four-petaled flowers that carry a heavenly fragrance of orange blossoms, it’s no question they caught the explorer’s eye.
In the home garden, mockorange flowers the best when it’s in full sun, but it does tolerate partial shade. As with any plant, building the soil with compost is always beneficial, but the mockoranges are generally adaptable to many soil conditions, as long as they’re not constantly in water.
While the native version regularly survives -40˚ conditions, there are ample hardy cultivars with features that add appeal for gardeners. ‘Snow White’ (Philadelphus xvirginalis ‘Snow White Sensation’, Zones 4–8) has a tidy, rounded shape and two-inch double blossoms, and it is known to withstand the heat of summer as well as winter’s cold. ‘Aureus’ (P. coronarius ‘Aureus’, Zones 4–7) adds golden leaves in the spring. These green up during the summer, alongside a profusion of white blossoms.
Cascades of Blossoms
Bridalwreath spirea (Spiraea prunifolia; Zones 3–8) is a completely non-fussy and durable plant, making its gorgeous display of flowing blossoms along the long stems even more impressive. As a bonus, the foliage turns an orangish-red in the autumn, offering another layer of interest to the landscape. Growing best in full sun, it still blooms in partial shade, although maybe not quite as prolifically. It does tolerate drought to some extent, and it withstands the heat of summer. (Editor’s note: Spiraea prunifolia has been reported as invasive in parts of the eastern United States; see http://www.invasiveplantatlas.org.)
While the standard version grows up to nine feet tall, there are more compact versions to tuck into smaller spaces. Look for ‘Snowmound’ (Spiraea nipponica ‘Snowmound’, Zones 4-8), which reaches just three to five feet high.