One characteristic that visitors often notice in a well-designed landscape is plants of varying heights.
Juxtaposing plants of different sizes is called layering. This practice generally involves using trees and tall shrubs as backdrops for smaller shrubs, perennials, grasses and bulbs. With experimentation, you can create layers in your own garden. It just takes some planning. And when plants don’t always grow as tall or short as expected, you have to do some plant shuffling. But fortunately, most plants are portable and relatively easy to move.
When designing a landscape, I think in terms of five layers:
Shade trees and large evergreens. These landscape giants grow about 30 to more than 50 feet high. Examples are honeylocusts, oaks, maples, Kentucky coffee tree, and American elm.
Ornamental trees and small evergreens. Plants in this category grow about eight to 25 feet high. Some of my favorites are autumn brilliance serviceberry, Tina dwarf crabapple, spring snow crab, Russian hawthorn, and golden raintree. As for small evergreens, I take their “mature height” on nursery tags with a grain of salt because most of them grow huge. However, the dwarf Alberta spruce grows very slowly and stays relatively small.
Medium/large shrubs and grasses. Here, I’m talking about shrubs and grasses that grow six feet or taller. Think of viburnums, rose of Sharon, chokeberries, serviceberries, Peking cotoneaster, redtwig dogwoods, tiger eye sumac, Cheyenne mock orange, bluestem joint fir, mugo pine, and Swiss stone pine, for example. Tall grasses include big bluestem, giant sacaton, and Miscanthus sinensis ‘Gracillimus.’ Don’t forget about vines, as well, to add height to your garden.
Small shrubs and grasses, tall perennials, and tall bulbs. Small shrubs and grasses can range anywhere from about two to five feet tall. One of my favorite plants in this category is blue avena grass, which grows about 2.5 feet high and wide. First of all, it isn’t as allergenic as most grasses. Second, it’s a four-season plant. Third, it’s blue, which is sometimes a difficult color to find in plants for the garden. And fourth, it looks fantastic with reds, purples, and oranges. Pair it with coral tulips in early spring and purple alliums in late spring/early summer.
Some easy-to-grow small shrubs are emerald mound honeysuckle, Pawnee Buttes sand cherry, meidiland ground cover roses, shrub roses, color guard yucca, Carol Mackie daphne, Genista lydia bangle, gro-low sumac, spirea, weigela, and leadplant, to name a few. The sand cherries, meidilands, and gro-low sumac make outstanding taller groundcovers, especially when you underplant them with shorter groundcovers.
Tall (as in two to five feet) perennials that dress up your garden include Joe Pye weed, hyssop, coneflower, shorter varieties of hardy hibiscus, daisies, asters, lavender, crocosmia, black-eyed Susan, oriental poppies, Rozanne cranesbill, bloody cranesbill, red hot poker, and tall garden phlox.
Bulbs that add height in the lower region of the garden are iris, daylilies, alliums, tulips, daffodils, frittilaria, Asiatic lilies, and dahlias.
Ground covers. This category of low-growing (one to two foot), spreading plants often gets short shrift in the garden, even though they provide continuity and help prevent weeds. You wouldn’t build a house without flooring, so why wouldn’t you want an underpinning for your garden?
I use Veronica pectinata as a fluffy blue carpet from which bulbs can emerge each spring. Other delightful choices include prairie winecups, orange carpet hummingbird, creeping phlox, Siberian bellflower, Angelina and other sedums, soapwort, candytuft, dead nettle, and creeping thyme.
If you haven’t thought about ways to layer plants in your garden, I encourage you to do so. You may find the results rewarding.