How many gardeners are slaves to their perennial borders, agonizing over ways to have several varieties in bloom from spring's first primulas to fall's last asters? Too many, if the number of times I'm asked for lists of long-blooming perennials is any indication.
Perhaps we've become too literal in how we define a border, assuming the best ones use only perennial plants. What we've forgotten is that Gertrude Jekyll, the great perennial-border designer of the late 19th and early 20th centuries, used deciduous and evergreen shrubs in her masterful gardens in England. In fact, if you look closely at the borders photographed for gardening books and magazines, you'll often discover a few workhorse shrubs among the drifts of billowing bee balm, daisies and phlox.
Integrating small shrubs into a border offers many benefits: they don't require the dividing, staking and deadheading many of our beloved perennials do, and they maintain their form and foliage throughout the growing season. Some perennials offer little interest when not in bloom; as the season progresses their foliage looks tatty or the plant simply disappears (as is the case with bleeding hearts), leaving boring gaps in the border.
Admittedly, some flowering shrubs bloom for just a few weeks (although potentillas and spireas seem inexhaustible), but their foliage shines on from spring through fall. Dwarf conifers and broadleaf evergreens hold the stage even in winter, when nothing looks more forlorn than a long, wide border of flattened and cut-back perennials. The woody forms of a few strategically placed shrubs—especially those with interesting stem colour, such as Japanese kerria or Tatarian dogwood (Cornus alba)—prevent the past-its-prime border from looking completely abandoned, flat and boring.
But what shrubs work best in a perennial bed? Obviously, size is a consideration—squeezing a large elderberry or lilac into a border through ruthless shrub pruning is not recommended. Fortunately, plant breeders introduce new compact shrubs each year, resulting in dozens of options.
When placing shrubs among your perennials, consider not just their overall height and spread, but also their shape. Some are prostrate and spreading, others upright; some form dense mounds, while others grow in a loose fountain shape. A well-designed border relies on more than flower colour. Contrasting textures, shapes and sizes of foliage all contribute interest, and this is where shrubs can shine.