Plan for some evergreen trees and shrubs for year-round color and mass. Scotch, mugo, and Japanese black pines, hollies, Japanese yews, pieris, mountain laurel, camellias, azaleas, and rhododendrons will flourish with some protection. Among the deciduous shrubs, privet, forsythia, spirea, firethorn, mock-oranges, lilacs, and viburnums have proved their worth.
Vines for Patterns
Vines cover bare walls and provide flower and foliage patterns. Wisteria is one of the best; but Japanese honeysuckle, bittersweet, the fast-growing Chinese fleece vine, Boston ivy, and Virginia creeper or woodbine are all excellent. English ivy, as a climber or ground cover, will hold its own on rooftops, though it must be kept out of strong winter sun in the North. Scarlet runner beans, morning glories, cypress vine, and moon flowers are annual kinds to try.
Roses for Fragrance
Every rooftop garden, even the smallest, should have some roses for color and fragrance, as well as their ability to take wind. Train some climbers over the walls and concentrate on such floribundas as Betty Prior, Pinocchio, Carrousel, Floradora, Spartan, Vogue, and Fashion. Miniature roses are ideal for small containers or for edging larger planters. You'll like the pink Sweet Fairy, the deep crimson Tom Thumb, the yellow Bit O'Sunshine, and Pink Joy. Rouletti, a rose-pink that is one of the hardiest, grows six inches tall.
Some perennials are essential, so make room for day-lilies, astilbes, iris, veronicas, shasta and painted daisies, balloon flowers, hostas and chrysanthemums. If climate allows, plan for spring bulb displays of crocus, hyacinths, daffodils, and tulips. During the summer all kinds of tender bulbs can be grown-dwarf dahlias, tigridias, gladiolus, montbretias, Peruvian daffodils, calla lilies, and fancy-leaved caldiums. Hardy lilies can be bought as pot plants in early spring for setting out in suitable containers.
Annuals will provide riotous color, so allow for some
of these-marigolds, zinnias, petunias, nicotiana, nierembergia, Madagascar periwinkle. (Vinca rosea), cleome,
snapdragons, annual phlox, verbena, dimorphotheca,
ageratum, and heat-loving portulaca. Coleus will thrive in shade, and heliotrope will give fragrance. Fuchsias and geraniums offer vivid splashes of color; and in the constant wind and intense sunshine of the rooftop, succulents and sedums are without peer.
The concentrated area of the roof garden offers opportunity to display attractive containers. There you can give prominence to a handsome decorated jar, a choice piece of glazed pottery, or a hand-carved wooden tub. On the wall, you might hang a bird cage filled with foliage plants or a hand-painted pot with grape or kangaroo ivy. Beside a doorway, place a glazed strawberry jar planted with sedums and succulents or an ornamental well-head with trailing grape ivy will be attractive.