Creating a pleasing border in our midwestern climate requires more than flowering herbaceous plants. Small shrubs offer a structure and size that most perennials cannot match in this region's short growing season. When the perennials vanish for the winter, shrubs provide a welcome presence.
Some of the best border choices are smaller shrubs with twiggy, thinner branches that fit nicely with the soft, loose feel of a perennial garden; summer bloomers that contribute to the sequence of blooming plants; and shrubs with variegated or colorful leaves.
Shrubs that compliment, not dominate, a perennial border
Spirea (Spiraea spp., cultivars 'Norman', 'Red Princess', 'Crispa', 'Goldmound', 'Little Princess', 'Neon Flash', 'Shibori' and others)
This group of small shrubs has leaves that open to various hues of red, gold, and yellow and usually fade green by summer. Flowers are white to deep pink and bloom in early summer. An added bonus is that late spring pruning prompts a new flush of reddish leaves in summer. Fall color is variable but can be a stunning purplish-red. The dense reddish-brown twigs are attractive in winter.
Variegated Japanese kerria (Kerria japonica 'Picta')
Kerria is an early spring bloomer with profuse bright yellow flowers that open with the midseason bulbs. Its delicate leaves have an attractive white edge, and its arching, free-form habit makes it a good combination with perennials. It prefers partial shade.
Kalm St. Johnswort (Hypericum kalmianum)
St. Johnswort has yellow flowers that bloom in midsummer. Its narrow leaves are blue-green. Plant it in full sun for best flowering.
Hummingbird summersweet (Clethra alnifolia 'Hummingbird')
This summer-blooming dwarf shrub has long panicles of white flowers that have a sweet fragrance and are a great favorite of bees. This shrub tolerates moist, shady conditions.
Crimson pygmy barberry (Berberis thunbergii 'Crimson Pygmy')
The main virtue of this small barberry is its deep red-purple leaves that color up best in full sun.
Arctic blue leaf willow (Salix purpurea 'Nana')
A fine-textured shrub, arctic willow has narrow blue-green leaves and a soft, loose habit. It prefers full sun.
Annabelle hydrangea (Hydrangea arborescens 'Annabelle')
If pruned to 12 inches from the ground every spring, this old-fashioned shrub works fine in a perennial bed. Its blowsy white flowers bloom in July and brighten from green to white and then fade to brown. Plant it in a partially shaded area with even moisture.
Henry's garnet sweetspire (Itea virginica 'Henry's Garnet').
When grown in full sun, sweetspire has handsome reddish-purple fall color. Its white, panicled flowers bloom in summer.
Purple smokebush (Cotinus coggyria 'Royal Purple')
Smokebush can grow to tree-size, but when pruned to the ground every year, it remains a small shrub with leaves of an intense purple-maroon. Full sun intensifies the color of the foliage.
Shrub roses (Rosa)
Hardy shrub roses need not be relegated to a separate garden bed. The more compact varieties that bloom all summer are preferred for perennial gardens. All roses perform best in full sun.
There are many possibilities for combining perennials and shrubs effectively in a mixed border. A visit to the Chicago Botanic Garden's Landscape Garden will provide inspiring examples for all gardeners.