The type of plants that make a garden look attractive and beautiful. It also describes the art of planting these perennials that bring out the richness in the garden.
I saw a Victorian house with two stands of giant plume poppies flanking its gates. The stately plants, six to eight feet tall, with their blue-green leaves the size and shape of fig leaves, were an unusual choice but they made an elegant frame for the wrought-iron gates, looking more like stalwart shrubs than the perennials they are.
We forget this about perennials-that many of them are tall enough to frame a gate, sculptural enough to stand alone, dramatic enough to be a focal point. Usually we think of them as growing only in borders, planted in drifts and prized for the color of their flowers and the season of their bloom. But many perennials offer much more.
These perennials do for a garden what trees and shrubs do: act as architectural components to create a framework or to define a space. And, like trees and shrubs, these plants come in a wonderful diversity of forms: rounded and arched, spreading and spiky, vertical and horizontal. But unlike slow- growing woody plants, which can take years to mature, perennials grow up fast. When I landscaped my own yard, I planted plume poppies (Macleaya Cordata) in spots where I ultimately wanted shrubs. (I would only plant this very invasive beauty inside a barrier like a metal collar- or in a large planter - to contain its rushing roots.) The Macleaya gave me the mass and volume I needed almost immediately and so kept me from tapping my toe impatiently while I waited for the shrubs to grow.
Crambe cordifolia, flowering sea kale, is another architecturally striking perennial. Clouds of baby's breath-like flowers billow above the dark green foliage, but after the flowers are gone the huge, puckered cabbage-textured leaves on tall stalks make a splendid addition to a garden.
A perennial I love and wish that I could grow in my garden is the sumptuous Melianthus major. At about eight feet tall, with soft, silvery serrated leaves, it looks like a small, languid ash tree. Its sculptural shape makes it ideal for marking a turn in a path because the plant seems to say, “Look here” or “Walk this way.”
The eryngiums- and there are many different kinds, from twelve inches to eight feet - are dramatic plants when they are flowering and just as dramatic when they are not. A bristly bract necklace frames the steel blue flowers and then the marvelous seed heads that follow. Even the silver-blue jagged leaves and blue-toned stems contribute to the impact these plants make.
Equally dramatic is Yucca filamentosa. Its coarse, sword like leaves support magnificent cremay flowers that rise to look us in the eye. Like all plants in the form of tall spikes or swords, yucca is dramatic, but it must be planted carefully where no one will accidentally bump into it. Its sharp serrated edges can be dangerous. New Zealand flax is much friendlier, but similar in mood and even larger. With smooth, gray-green leaves that grow to nine feet, it is striking when planted next to a garden step or to define the transition from terrace to garden. And Iris pallida 'Variegata,' with cream-and-gray sword-shaped leaves in the shape of a fan, offers pure Art Deco elegance.
Rounded leaves, on the other hand, no matter how large, seem soothing and serene. In a woodland garden try Ligularia dentate 'Desdemona.' Its flowers - bright orange daisies - are almost tropical, as are the big, rounded leathery leaves. The ornamental rhubard Rheum palmatum 'Atrosanguineum,' a perennial growing to three feet high and six feet wide, is often used as an accent among less striking plants. Its deeply cut leaves start out red and remain red on the underside even after the top has turned glossy green.
Like almost every gardener I know, I have learned much about designing with these architectural perennials - and particularly about using them in large masses. Another grass that is planted sweeps of low-growing Bergenia Cordifolia punctuated by the tawny, delicate stalks of maiden grass, Miscanthus sinensis 'Gracillimus.' The grass sways gracefully above the thick paddle-shaped leaves of the bergenia. Nearby is another of their signature plants, Sedum x telephium 'Autumn Joy.' From August on, its thick, succulent leaves and tight, rounded flowers look like a sea of ruddy bronze in an irregular frame of sword-shaped yucca leaves.
A garden that is pretty with flowers can be wonderful for a while, but every garden needs plants that hold their own when the flowering is over.
