NEW YORK - As the mean streets of many cities undergo a renaissance into vibrant downtown meccas, rooftop and terrace gardens, largely invisible to the public eye, are creating a verdant canopy.
Once wryly referred to as "tar beaches," hot, windswept apartment roofs have morphed into urban oases, replete with overflowing pots of annuals and perennials, herbs, vines and even fruit trees or walls of shrubbery.
"The increase in rooftop gardens is definitely a growing trend. Roof gardens are sprouting up in cities all over," said Laura Yip, who chronicles her adventures in urban gardening at nycroofgardenproject.blogspot.com.
Luxury condos are installing "green roofs" as an amenity, while enhancing energy efficiency, and locavore movement chefs lovingly tend to their herb and vegetable crops to spike their sauces and grace their artisanal pizzas.
But urban horticulture doesn't come easily. Outdoor space can range from a tiny balcony to sprawling aeries with dining areas, outdoor fireplaces and trickling waterfalls.
Growing a mix of thriving plants in the harsh conditions of most city rooftops takes planning, dedication, time and money. But it's still a bargain compared to the cost of a beach house.
"I would love to have a yard," said Amy Karafin, who maintains pots of annuals, herbs and perennials on her small terrace in Brooklyn. "The soil and watering situation are so much easier. Gardening with pots requires a lot more care and creativity.
Karafin said her plants dry out quickly and keeping the soil pest-free requires effort. But there are upsides, too.
"In New York, a garden usually means a shade garden, and I like my sunny terrace," she said. "It's more like an open-air room full of awesome plants."
Weeds, the bane of most gardeners, are also less of a problem.
"Container gardening is a much more controlled environment, and weeds are less likely to find their way into a roof garden," said Yip. "And those that do are easy to pull out."
Treasured green spaces
Amber Freda, who specializes in roof garden design, installation and maintenance, said in cities roof gardens are some of the most treasured green spaces.
"Roof gardens are like little secret jewels hidden out of reach in the clouds, nestled between skyscrapers and birds," she said.
Watering is often the biggest challenge. For gardeners without an irrigation system, it can mean lugging water up stairs or running a hose from the kitchen or bathroom sink.
And for anyone who travels regularly, keeping plants healthy often requires daily attention. Mike Roselli curtailed the plantings on his Washington balcony this summer because of frequent absences.
"Even though I usually have it planted with sedum and other drought-tolerant plants like agave, it just bakes in the Washington heat."
Roselli said experience is the best teacher.
"Slow-growing plants that don't need much water work best. I gave up on flowering annuals a long time ago," he said.
Less-than hardy herbs such as basil and parsley also tend to go to seed quickly if not regularly tended. Roselli also relies on tricks such as small-leaf ivy, which spreads its tendrils among his other pots, keeping them shady and cool.
Knowing the space, including how much direct sun it gets and whether it will be exposed to strong winds, is another key to success.
"Roof gardens have to deal with extremes in temperature and high winds that can quickly shred large-leaf plants not suitable to life atop a mountain-like rooftop," Freda explained.
The amount of sunlight will dictate whether you'll have a bumper crop of tomatoes or a hedge of hostas. In an exposed area like an open rooftop, experts say hearty shrubs and bushes, fruit trees, junipers and grasses can withstand strong winds. But in a sheltered area, you might forego staking tall-stemmed, top-heavy flowers such as lilies or peonies.