Top 10 perennials to add dynamic layers to the garden

Most home gardens would be far more interesting and enriching if we simply upped the number of plants in them. We have too much lawn, too many areas of mulched beds and too limited a range of plants to carry the landscape through the growing season and beyond.

In any landscape development, perennials play a vital role in providing the layer that is both colorful and structural, especially when used boldly as a massing or ground cover. Perennials die back each winter and then regrow from the roots. From their spring emergence, seasonal flowering and gentle decline, perennials provide the most dynamic layer in the garden. Some perennials, especially ornamental grasses, carry a measure of beauty through the winter even if their top growth is lifeless at that point.

Perennials arguably represent the single most exciting aspect of horticulture in our time, because they fit so well with the idea of creating gardens that are not only beautiful but provide shelter and food for wildlife and help to address environmental issues such as protecting soil, checking storm water pollution and reducing the need for pesticides.

With help from Roy Diblik of Northwind Perennial Farm in Burlington, Wisconsin; the New York Botanical Garden’s Kristin Schleiter; George Coombs, research horticulturist at Mount Cuba Center in Hockessin, Delaware; and Elise Zylstra of Sandy’s Plants nursery in Mechanicsville, Virginia, I came up with a list I call the 10 best perennials you’ve never heard of. Consider them when reworking garden areas in late summer and early fall. Some are for areas of full sun, some for shade, and most will work in areas of light shade.

Tricyrtis

The tricyrtis or toad-lily is interesting on two counts. First, it blooms late, in September and October. Second, the flowers are strangely invisible until you study them, when they reveal themselves as extraordinarily exotic and orchidlike. Some varieties bloom in the leaf joints, others at the end of their arching stems. The variety Sinonome is one of the latter and is valued for its maroon markings on creamy white blossoms. Place a clump of tricyrtis at the edge of shade garden paths, where they can be admired. They grow to three feet and should be spaced 18 inches apart. Because they grow and appear late, they can be interplanted with other woodland perennials and small shrubs.

Oak sedge

Sedges are low-growing, grasslike perennials that flourish in difficult situations such as dry shade or wet soil, depending on type. Most prefer partial to full shade. Grown in masses, they make excellent alternatives to such boring groundcovers as English ivy, liriope or pachysandra. They can also be squeezed in between other herbaceous plants as textural highlights. I am partial to fine-leafed sedges that will adapt to dry conditions once established, such as the oak sedge, botanically Carex pensylvanica. The wispy plant is a fresh green and grows to about 10 inches.

Blue grama

This is another fine-textured, native ornamental grass for full sun. Blue grama (Bouteloua gracilis) forms clumps of upright blades topped with straw-colored seed heads that age to brown-purple. They are held horizontally to the stem and quiver in the slightest breeze. The grass grows to about 15 inches and needs an open and well-drained location. Use it to edge paths, as filler or as an accent. Blonde Ambition is a showier variety.

Cranesbill

Cranesbills, or hardy geraniums, have been gaining popularity over the past decade, but they deserve greater use in their attractive and unfussy role as fillers and ground covers, and work in areas of full afternoon sun or partial shade. I have had consistent success with a species named Geranium macrorrhizum and grow one named Ingwersen’s Variety. It has a muddy pink flower in late April and May. It works as a ground cover in partial shade and will take dry conditions once established. In shadier beds, a coarser native species named the spotted cranesbill (Geranium maculatum) is a sturdy choice, with lavender blooms throughout May.

Barrenwort

Barrenwort — often called by its botanical name, Epimedium — is another perennial that is gaining steam and should be in every garden with light to heavy shade. Its early-spring blooms are delicate and interesting. (For good display they rely on the gardener removing the previous year’s foliage by March.) But the real value of this plant is its clean and lovely mounded clumps of heart-shaped leaves. Its other virtue is that it is one of the few perennials that will adapt to dry shade, though it will take longer to reach a good size (four years or so) in such a location than in the optimum conditions of richer but well-drained soil.

Prairie dropseed

Prairie dropseed (Sporobolus heterolepis) is a soft, mounding grass that remains fresh and green until the fall, when it turns a beautiful shade of burnished orange. In high summer, its clumps are topped with a haze of flowering stems that perfume the air with a scent reminiscent of bruised cilantro. It can be planted as a filler or accent in a sunny bed. It takes three to four years to reach its mature size of three feet high and two feet across.

Yellow false indigo

False indigo (Baptisia australis) is a shrubby perennial that makes a fine addition to the garden, with gray-green leaves and spikes of lupinelike blooms, a deep indigo blue, that appear in May on plants that are already three to four feet high. The yellow false indigo is another species (Baptisia sphaericarpa), but it is smaller and tidier and is covered in shorter spikes of bright yellow blooms in late spring. A number of varieties have been introduced, including the particularly floriferous Screaming Yellow. Use it singly or in small groups as a filler plant or accent, in full sun to light shade. It won’t work well in moist soil.

Slimleaf ironweed Iron Butterfly

Common New York ironweed is a tall and somewhat rangy wildflower of damp meadows that is valued for its sprays of purple flowers in August and September. Slimleaf ironweed is another species (Vernonia lettermannii) and grows to about three feet in height and spread. In late summer, it is smothered in small purple flowers that are magnets for butterflies. Until then, it looks tidy and compact, with dark, fine-textured foliage that makes it a great foil for other perennials. Diblik pairs it with prairie dropseed in a hot dry setting. Iron Butterfly is a selection that is more compact and densely flowered, growing about three feet high and two feet across. As with blue grama, vernonia needs a sunny location.

Calamint Montrose White

The calamint (Calamintha nepeta) is an aromatic, ornamental mint that calls to mind the gray-leafed, blue-flowered mounds of the related catmints of early summer, except the calamint produces masses of small white blossoms all summer long. It draws a host of pollinating insects and hummingbirds. The variety Montrose White corrects a couple of disadvantages of other calamints: It is somewhat compact, though can still spread to three feet, and the flowers are sterile, so it doesn’t seed about. It grows in full sun or partial shade but does require free-draining soil, which is especially important during winter dormancy. Use calamint as a filler in a sunny border, as an edging plant along paths (for its aroma) or in a container.

Tufted hair grass

This is a handsome mid-size native grass valued for showy seed heads that provide ornament from summer into fall, when the foliage turns a bronze color. Its botanic name is Deschampsia cespitosa. The stalks move in the breeze, giving a kinetic quality to the grass. Goldtau (German for “golden dew”) is a variety that was selected for its more compact habit and the yellow cast to its inflorescences. It grows to 24 inches with a spread of about 30 inches and should be used as an accent grass or in drifts in a larger border.

Perennials tips

There is no single source for all 10 of these, and some plants on this list will be easier to find than others. Some may not be available until early spring, but be patient, because these cultivated varieties are worth seeking out. The cost of multiple perennial plants can add up. There are ways to handle this:

• Tackle single, manageable areas of the garden once or twice a year. Don’t seek to transform the whole garden overnight.
• Do the work yourself, including lawn reduction, bed clearing and soil preparation in advance of planting.
• Buy the smallest sizes you can find, but make sure you space plants for their eventual girth, even if the planting looks thin for a year. Most perennials reach a mature size in three years.
• Weed regularly between growing plants.
• Look for end-of-season plant sales.
• Driving to a distant nursery can save on shipping costs and can make for a pleasant day trip.
• Native plant societies hold periodic sales with good prices on perennials, sedges and grasses.