The Joys of High-Rise Horticulture

Whether you have a sliver of a balcony or a sun-drenched rooftop terrace, you can turn your aerial bit of the outdoors into a unique and personal garden in the clouds.

Too many people think that a small balcony has no better purpose than to sport a couple of cheap plastic chairs and a plastic table. But your slice of outdoor living can actually provide a dynamic living window on the world. Nondescript wrought-iron or aluminum railings can be set ablaze with stunning vines, decorative planters, hanging baskets, and maybe even a hummingbird feeder.

Imagine looking out your sliding glass doors through a tropical “window” created by hanging baskets with trailing vines in full bloom, along with attractive containers filled with sweet-scented vines twisting sensuously upward. Even if you overlook a parking lot – or other apartments – your view will be handsomely colored and enhanced by the foliage and plants which form a botanical picture window.

For example, a neighbor in Arlington routinely trains the tropical Mandevilla ‘Alice du Pont’ around the sides and front of her modest balcony. People routinely stop and stare up at her third-story flat, shielded from the southern sun by twining vines of large, glossy, deep-green leaves and enormous trumpet-shaped clusters of four to five inch-long hot-pink flowers, which bloom from spring through late summer and fall. Amazingly, her jungle canopy all sprouts from pots and baskets less than six inches in diameter.

Bear in mind that Mandevilla, like many of the tropical plants you may choose to employ, from ficus and ferns to dwarf orange trees, will need to overwinter with you indoors – or be replaced each year. Personally, I abhor letting perennials perish, and further welcome the touch of green in my indoor plantscape during the rainy, grey days of winter.

My own rather expansive rooftop oasis features unattractive wrought-iron and wooden railing. As a renter, I cannot change the materials – but I can certainly hide them. A large, 18-inch pot has comfortably housed a native wisteria vine for almost a dozen years. The vine covers more than 20 feet of railing and blooms profusely every spring. It is joined by 12-inch containers filled with trumpet vine and aromatic virgin’s bower, which cover much of the remaining railings, along with heirloom terracotta pots boasting a variety of fragrant jasmine varieties. Fortunately, only the jasmine plants are taken indoors in winter.

But there is much more to landscaping a roof or balcony than viney cover-ups. With proper exposure and good soil mixes, it is possible to grow most of your summer vegetables and herbs, from Ancho peppers to trellised zucchini, and all the tomatoes, lettuce, basil, and dill in between. Be sure to underplant your larger vegetables with parsley and tasty, brilliant-flowered nasturtiums.

Culinary herbs such as thyme, sage, oregano and rosemary, are readily grown in six to eight inch terracotta pots and set on a decorative étagère or tiered-plant stand. The neat organization will create an atmosphere of Provence, even if you can hear the Interstate in the distance.

There are some specific considerations for rooftop gardening which are best addressed before you begin planting. Watering can become a major chore if you cannot readily hook up a hose to an outdoor bib. I began my garden 25 or so years ago like Gunga Din, each day hauling buckets of water out to my garden. Soon after, I invested in a two dollar attachment for my bathroom faucet, screwed on a conventional garden hose, and have been watering hundreds of plants effortlessly, usually in less than 15 minutes.

Newcomers to atmospheric agriculture can now easily buy coil-style hoses for added convenience and simple storage. You will need the convenience because balcony and terrace gardens are almost exclusively container gardens, and containers, which are limited in their ability to retain soil moisture, need almost daily care.

Wind is another concern. Wind hastens evaporation, leaving plants thirsty, and can also make exposed areas terribly cold in winter, which can damage the roots and foliage of even tough perennials. During the winter, I have often moved my more cold-sensitive plants against a south-facing brick wall and huddle them together. I also try to remember to water them occasionally throughout the winter, especially during long periods of drought.

Also, be sure to adequately secure any taller specimens to prevent them from being blown over. While any number of ornamental conifers, lacey-leafed Japanese maples, crepe myrtle, and other small trees and shrubs thrive in fair-sized containers, their branches can easily catch a gust of wind, leading to a nasty tumble and damage to plant and pot alike.

For larger projects, such as a small water garden, pergola or permanent planter boxes, be sure to consult with an architect or structural engineer. Wet soil, evergreen shrubs, cast iron urns, small trees and the like, especially en masse, can create a significant load on your rooftop or balcony.

Fear not! After tackling the basics, the rest of your project is pure fun – or even fantasy. With an attractive arrangement of outdoor furniture, miniature white lights haphazardly draped through your shrubs or along your railing, and a burbling tabletop fountain, your terrace can become a vital outdoor living space, perfect for entertaining or just unwinding with a glass of wine.

You can use trellises set into planters, covered with passionflower vines or coral honeysuckle, to screen off your balcony from nosy neighbors or hide unsightly heat pumps. Similar trellis structures, or ornate pots with topiary shrubs, can also be organized in larger spaces to define special areas, such as a sun deck with lounge chairs, or an al fresco bar or dining room. With weatherproof speakers, you can even create a dance floor, unless the people downstairs object to midnight jitterbugging.

Additional structural elements like redwood arbors can support climbing roses, night-brightening moonflower vines, and transform a flat rooftop into an intimate personal landscape you may well prefer to indoor living. It has certainly worked such magic for two high-rise horticulturists, especially as we continue renting the same rooftop apartment overlooking Washington and dancing the nights away.

Copyright 2009, Joseph M. Keyser