Herbs for the Rooftop
By Doree Pitkin
Hyssop among the high-rises, basil above bricked streets, and home-grown lemon verbena for tea–the rooftop herb garden defies the notion of the bleak, anonymous city. In this rarefied atmosphere, the sensual qualities of herbs are perhaps more treasured than they are on earth, where they are more easily won. Stepping outside one’s door to snip fresh basil may be a greater pleasure on the nineteenth floor than at ground level, and the scent of lavender more intense in the night air high above the usual diesel fumes.
The challenges of creating such a city oasis are matched by its satisfactions, attests Linda Yang. A Brooklyn native, she was an architect before she found her way into the garden. She began when a neighbor in her apartment building asked her to look after some houseplants on the balcony. As Yang tended them, she grew aware of the potential for raising plants in that small space.
Yang has gardening in her blood; her earliest memory is of her father clipping lush red roses and placing them in a black glass vase. She also enjoyed cooking with fresh herbs, though at the time of her plant-sitting stint, only a few were available year-round to city dwellers. Herbs, then, were an obvious choice for her first garden.
Since then, Yang has combined practical experience with solid research. She is the author of numerous articles on urban gardening and The City and Town Gardener: A Handbook
for Planting Small Spaces and Containers. She also wrote a New York Times garden column for sixteen years. Throughout her career, her gardens have flourished, with herbs abundantly included among trees, shrubs, annuals, and flowering ornamentals.
The essentials: light, water, and soil
Urban high-rise gardening spaces range from blocky balconies and sunny terraces to wide, shady windowsills and steaming patches of asphalt roof; Yang has dealt with many. Despite their differences, she notes, all garden spaces require light, water, and soil. Supplying these necessities is often the urban gardener’s first job.
Up on the roof, Yang points out, light seldom qualifies as “dappled,” as it might be when under a small-leaved shade tree. Instead, it’s either direct sun or deep shadows thrown by other buildings, the balconies above, fences, or dividing walls. Depending on the time of year, a potential garden space may be in full sun only briefly, and some corners may be in constant shadow. Light may be reflected off the windows of a neighboring skyscraper. Yang recommends careful observation and recording where and when the sun falls on a proposed garden area.
Linda Yang’s easy planting mix recipe:
1. Measure the height of your container.
2. Mix equal parts of bagged topsoil, perlite, and peat moss. For each 6 inches of container height, add the following:
3. A trowelful of composted cow or other dehydrated manure a handful of granular fertilizer.
4. Mix well.
Don’t count on rainfall to provide the regular, frequent drenching that herbs in high-rise container gardens need for best growth, especially during hot weather. The plants can’t spread their roots horizontally to capture rainwater, and the surface area of the containers’ soil is small. Spaces designed for outdoor living may be equipped with water spigots, but improvised garden spaces often lack this luxury. Snaking a hose from an indoor tap out the door or window to the garden area brings the water to the plants and certainly beats lugging a watering can.
No soilless mixes for Yang, who insists that soil, with its living microorganisms, should be a component of her potting medium. “No life, no soil,” she says. Instead, Yang developed her own lightweight and hearty planting mix (see sidebar above). In doing so, she developed yet another urban gardening skill: the ability to ignore the stares of neighbors as parfum de cow fills the elevator.
Lightweight containers are necessary for herbs on high, to save both the floor and the gardener’s back. Fiberglass and plastic ones are very good. Yang’s smallest containers measure about 16 inches in height and depth, and the largest 24 inches; each pot has several drainage holes.
Herbs to grow
For nearly every growing condition, there’s an herb that will grow happily–but is it an herb you want to grow? “If you can buy the herb ready to use from the grocery store, use your space for something unique,” advises Yang, who skips ordinary mints but dotes on a delicious orange mint unavailable in stores. Because her family favors garlic chives over regular garlic, she grows them for use year-round.
Quirks of rooftop gardening
A breeze on the street can be a howling gale several stories up. Your herbs may need a sturdy windbreak of fencing or shrubbery; certainly they need extra water to counteract the drying effects of the wind.
Much urban pollution these days is dirt and grit. Spray your plants regularly with plain water to clean them and maximize photosynthesis.
Nearly everything that bugs earth-bound gardens can bug yours, too–aphids, gypsy moths, thrips, spider mites, even grasshoppers–and they’re treated the same on the rooftop as elsewhere. On the other hand, you’ll also get beneficial insects such as ladybugs, honeybees, and perhaps an occasional praying mantis.
Not all rooftop gardens receive six to seven hours of sun daily, so Yang doesn’t take “full sunlight” recommendations literally when it comes to growing herbs. She has successfully grown a number of sun-lovers–including rosemary, oregano, basil, and tarragon–in less light. “These plants wouldn’t win any prizes from the local horticulture society, of course,” she says, “but they produce fresh and tasty leaves just the same.” A few herbs–nasturtiums, for instance–demand full sun to flourish.
Yang also experiments with the hardiness of perennial herbs. “If it’s hardy in the ground in your location, it should be hardy in a container,” she asserts. If an herb fares poorly over winter, out it goes. Herbs that consistently droop in the heat, wither in the wind, or fail to pop up in the spring are replaced by other, more durable kinds.
“My herbs get tenement housing,” Yang says with a chuckle. “For an immediate lush, dense look to my garden, I plant them closely together.” Many herbs don’t mind a bit; bee balm, sweet woodruff, and lemon balm easily crowd in among other plants, contributing color, fragrance, and flavor.
Playing it safe with sky-high gardening
Always hang railing planters inside the railing and hanging baskets over your floor space, thus minimizing injury if they should fall.
Place the heaviest containers where the floor is strongest: close to the building’s supporting walls.
Avoid using harmful pesticides, which can drift from your garden down to the street.
Spraying with plain water will dislodge many pests; use an insecticidal soap solution if an infestation is severe and water doesn’t do the trick. Building leaks to structures down below are the bane of urban gardeners. Check for leaks before starting a garden and frequently afterward.
The rooftop garden in winter
When the first frost strikes, Yang heaps over her containers the leaves fallen from the trees in her garden, and later, Christmas tree branches. If the weather cooperates, she shovels snow on top of the soil; it protects the plants from wind, insulates them from temperature swings, and melts gently when moisture is needed.
Other winter chores are few in the urban garden, but watering must be continued throughout the season–more container plants die from desiccation than from cold, Yang suspects. “If there’s been no significant rain or snow for several weeks, water in early morning when the weather is above freezing. Drench the soil thoroughly with cold water,” she says.
While the rooftop garden rests, Yang stocks up on supplies, visits flower shows to see what’s new, or snuggles up with a pile of garden catalogs. After a busy year, early spring planting dreams mark the beginning of a new rooftop garden season.
Doree Pitkin is an assistant editor of The Herb Companion and an herb book editor for Interweave Press in Loveland, Colorado.
Proctor, R. and D. Macke. Herbs in Pots: A Practical Guide to Container Gardening Indoors and Out. Loveland, Colorado: Interweave Press, 1999.
Yang, Linda, ed. The City and Town Gardener: A Handbook for Planting Small Spaces and Containers. New York: Random House, 1995.
——. Plants for Problem Places: Dependable Species for Difficult Garden Spots. New York: Houghton Mifflin, 1997.
——. The Town and City Gardener. New York: Brooklyn Botanic Garden, 1992.
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