Urban Rooftop Gardens

Walk the jungle streets of New York City and you'll find the lack of land doesn't stop city gardeners. No yard? No problem. Options include window boxes, tree beds, vines up a fire escape, ornamentals along sidewalks or steps and rooftop gardens.

From Seattle to Soho, Barbara Hobens Feldt is the go-to gal when it comes to urban gardening. So, what's the trick to rooftop gardening? Containers, she says. From vegetables to herbs, perennials and annuals, what you can grow atop a roof is only limited by the elements. And, while cramped city living can be a drawback to humans, most plants don’t mind cozying up.

"Plants love to be together. They love the closeness and the overlapping—they actually seem to thrive on it," says Barbara. Because a lot of rooftops get full sun, it's keeping your plants moist that proves a challenge. Barbara recommends putting your finger into the soil to check for moisture.

Vegetables in particular need to be kept moist, but because they love sun, a rooftop is the perfect place for them. To keep the veggies company, sun-loving perennials and annuals make a colorful addition while attracting beneficial insects. "You can add almost any flower to your garden," says Barbara.

But you aren't completely limited to sun-loving plants. "Even on a rooftop, there are an incredible number of microclimates," says Barbara. "Shifting a plant in front or behind can move it from full sun to partial shade and give it exactly what they want."

Shade takes on a whole new meaning in the city. "When you have shade, you don't have dappled shade from a lightly flowing tree. You have major shade created by buildings," says Barbara. But even the complete shade created by a building can support lush woodland-type plantings. Japanese painted ferns or hostas can liven up a concrete jungle.

If container gardening is your rooftop choice, there are a few tricks to remember—starting with weight considerations. Plastic containers are useful because they don't add a lot of weight to your roof. Mobility is important, too. A saucer on wheels will make it convenient to rearrange plants based on their specific needs.

Be sure to check for holes in containers. You need enough holes for proper drainage, but not too many or the container won't retain moisture. Lacing pieces of broken terra cotta on the bottom will help to keep soil in place and allow drainage.

The type of soil you use also adds weight. Try a soiless mix that's part perlite and part vermiculite. "It's fluffy, it's happy and it won't add a lot of weight to your roof deck," says Barbara. She adds compost to her containers along with the soil, so as the plant roots grown downward they get an extra boost of nutrition.

Barbara chooses to plant rosemary (an annual in New York City) for its beauty and benefit as an herb. She adds Japanese grass, a sweet potato plant for color and texture and a small vine. She tops it off with some mulch to conserve water and hold down weeds. A container like this one will last until the first snow in December.

One last tip from Barbara: Because space is precious in the city, planting up instead of out is a great way to grow. Consider growing up trellises, fire escapes and even buildings, using hanging baskets and plant-packed window boxes.

But before gardening in any shared space, ask for permission as a common courtesy. You'll be enjoying your rooftop oasis in no time.