Up in the Air: Rooftop Gardens
It isn't enough that rooftop gardeners have to worry about the weight of potting soil and how many elevator trips it will take to schlep two bags of amendments, a flat of marigolds and a small crabapple tree. They also have heat, drought and drying winds to worry about. Whether your garden is 12 stories up or on a backyard patio, their advice can help you cope:
Make smart plant choices
"A rooftop garden is exposed. It's almost like a beach environment — hot, dry and windy," says Carmen DeVito, a landscape designer in Brooklyn, N.Y. "So I use a plant palette like I would at a beach house." In her rooftop designs, she uses bayberry (Myrica pensylvanica, a common coastal plant), roses (especially 'The Fairy'), herbs, grasses (Miscanthus sinensis 'Yakujima'), succulents, yarrow, pines (like Pinus mugo), dwarf junipers, cotoneaster and Russian olive.
Lots of rooftop gardeners grow tomatoes, coleus and other thirsty plants. If you know you're going to be able to water once or twice a day as necessary, go for it. If not, choose drought-tolerant plants such as lantana, portulaca, euphorbia and grasses. Mediterranean-type plants, including herbs like rosemary, lavender and thyme, also withstand drought.
Look especially for heat tolerance in your plant selections. Plants like Dahlberg daisy (Dyssodia tennuiloba), globe amaranth (Gomphrena globosa) and gazania (Gazania rigens) regularly make the "hot" list.
Also seek plants that don't need to be deadheaded or that create much litter. If you're gardening in a spot where a compost pile isn't possible, the less maintenance you have to do — and the less debris you have to get rid of — the better.
Provide some shade if you can
The ambient temperature of an urban setting builds up as heat is absorbed and reflected from a jungle of hard, concrete surfaces. If you can, grow vines up a trellis, add a patio umbrella or even build a pergola to reduce the amount of sun shining on your garden floor. "Or you can construct shade with metal posts and sailcloth," says Joan Grabel, a landscape designer in Studio City, Calif.
Provide water and good drainage
Install an irrigation system, especially drip irrigation, says DeVito. "Watering is the single most important gardening chore, and on a rooftop you may have to water up to twice a day." With an irrigation system, all you have to do is set a timer to water and check the system periodically.
If you don't have an irrigation system, remember the rule of watering — water well whenever you water. It takes time for potting soil to fully absorb water, so water slowly or rewater about 30 minutes later.
Account for drainage. Direct runoff away from the main area where people will gather.
- Use larger-sized containers rather than smaller ones. They retain moisture better, plus they're heavier in weight (so they're less likely to topple over in the wind). With fewer but larger pots, says DeVito, "there's easier maintenance, less evaporation and a cleaner look." Containers limit rootball size. As long as the plant gets enough water, it will adapt.
- Use a lightweight soil mix designed for containers — one that includes perlite or vermiculite. DeVito uses a mix that has shredded bark, vermiculite and peat moss, and then adds pure compost to the mix.
- Use organic fertilizer so nutrients don't leach out as quickly. Slow-release fertilizers are a good choice.
- Mulch the soil surface to conserve moisture and keep soil temperature consistent.
Rooftop (or balcony or deck) gardeners have to consider how much weight the structure can support. If you're planning to do some significant gardening or hardscaping, says DeVito, "work with the building engineer and review the building codes to see what's allowed. Codes limit what types of materials can be used." If you're renting, you probably won't be able to (or want to) provide any structural reinforcements.
Green Zone in the Clouds
One of Montreal’s most historic hotels, Fairmont The Queen Elizabeth is especially unique for its self-irrigating edible rooftop garden where vegetables, herbs and over 400 edible flowers grow for the three on-site restaurants.
A Bird's Eye View
Open to the public with tours and lunch on specific days, the rooftop garden at New York’s Waldorf-Astoria is located on the 20th floor and includes designated raised beds for fig and apple trees, hops, strawberries, herbs which are used by the hotel’s executive chef for meals. Local honey is also produced here by the more than 360,000 European honeybees that live in the hives.
Green Space Amid the Asphalt
On the 8th floor of the Hilton Chicago is a thriving kitchen garden consisting of 83 EarthBoxes (plastic containers with a built-in irrigation system) which contain such edibles as tomatoes, fennel, peppers, radishes, herbs and more.
A Visit to the English Woodlands
Mulberry trees, Japanese maples and other plant and flower specimens adorn the grounds of this unique green space at The Rooftop Gardens in London which also includes wildlife and water features.
Nob Hill's Best Kept Secret
Situated 100 feet above Powell Street in Nob Hill is a lovely rooftop oasis at the historic Fairmont San Francisco. Offering sweeping views of the city’s skyline, the garden is distinguished by its central fountain and distinctive palm trees.
Although it is not open to the public, the rooftop garden at Fairmont The Queen Elizabeth in Montreal provides the kitchen with an excellent array of organic vegetables and herbs for the guests such as plum tomatoes, Swiss chard, endive, zucchini, mint, basil and even edible flowers.
This stunning overview of the 2100 square foot rooftop garden at Fairmont Waterfront in Vancouver, Canada is representative of green space/edible garden initiatives that are taking place in luxury hotels in cities around the world. First created in 1996, this garden produces over twenty varieties of herbs, fruits, edible blossoms and vegetables including pumpkins, carrots and kale.
Abundant beds of rosemary are among the many herbs and edible plants being raised in the rooftop garden of the Fairmont Express in Victoria, Canada. Located directly above the front lobby, the garden also includes other sustainable plants from Vancouver Island.
At the top of City Hall, an eleven story office building in the Loop, is Chicago’s most famous rooftop garden. Consisting of over 20,000 plants of more than 150 species, this green space is an inspiring model for other major cities because it helps improve air quality, reduce storm water runoff and minimize the urban heat island effect.
A Future Trend
It might look like a futuristic landscape but this unique rooftop garden at the Ritz Carlton Charlotte is a field of sustainable vegetation that serves the local bee population and provides honey for the kitchen chefs.
Turning rooftops as green as possible only makes good environmental sense, says David Yocca, landscape architect and planning director of the Conservation Design Forum in Elmhurst, Ill., a firm that designs ecoroofs. The ecoroofs are lined with special materials, topped with a lightweight blend of soil, compost and perlite, and planted with anything from small grasses to eight-foot conifers. Irrigation systems on timers dispense water on a regular basis.
"It's good from an ecological and human health standpoint," Yocca says. "It's a way to manage [runoff] in a positive way and it minimizes chemicals."
Plus, plants evapotranspire, Yocca explains, and that "creates natural air conditioning, so you don't have an urban heat island. An ecoroof protects the building against heat loss in winter and heat gain in summer." Since plants convert carbon dioxide into oxygen, ecoroofs also improve air quality. In several cities, ecoroof advocates like Yocca are working to have green roofs become common practice. In Europe, they're already fairly common; in Switzerland new buildings are required to have on their roofs the same amount of vegetation they replaced.