Vertical gardens appeal to urban green thumbs

Things are looking up for gardeners who are short on space but long on imagination.

It's increasingly easy to build vertical gardens, structures that enable plants to grow upward if there is no room for growing them laterally.

These living walls can make great backdrops for mixing color with cuisine; use them to frame patios and decks with tapestries of miniature tomatoes and spaghetti squash. Or make privacy screens by draping morning glories, clematis, and sweet peas over netting or latticework.

"Vertical gardening makes it easier to have your ornaments and eat them, too," says Leonard Perry, an extension professor of horticulture at the University of Vermont. "Grab a tomato or two as you walk by, which is an easy thing to do when they're hanging at different levels."

Living walls entail gardening on the edge, however. While great for saving space, they are more challenging when fertilizing and watering.

"Holding water on a flat roof isn't difficult, but turning it 90 degrees on a wall is tremendously tricky," says Edmund Snodgrass of Street, Md., an author and operator of a nursery dedicated to producing green roof plants.

"You have to decide early on what it is you want to accomplish with this. Understand what level of effort you want to put into it as a homeowner."

Living walls vary greatly in size and sophistication, from commercial designs with complicated plumbing and roots attached to walls, to plant pockets connected to webbing, to flowering vines planted in the ground and trained to climb homemade supports. Each needs a sturdy framework, waterproofing material to protect the walls, and plant containers.

"Walls with pockets are nice for urban areas or properties with elevation changes," Mr. Snodgrass says. "They're also easy for backyard gardeners to use because they don't need complex irrigation systems. All have their merits."

More benefits of vertical gardens:

—Erected against warm walls, they can become microclimates resistant to killing frosts. "That can mean starting your garden earlier in the spring and continuing with it later into the fall," says Derek Fell, a horticulturist from Pipersville, Pa., who has developed a backyard device he calls the "Skyscraper Garden." ''Climbing plants like spinach or pole snap beans will bear all summer, giving you up to 10 times the yields of similar bush varieties."

—Plants grown in vertical gardens are less disease-prone. "Having them grow upright gets more air circulating around them," Mr. Perry says. "Less accumulated moisture means less disease."

—Little or no stooping is required. "Forget all that bending over as you plant or prune," Perry says. "Everything is conveniently in front of you."

The weight of a maturing vertical garden can fracture or rot buildings if it's not installed properly, however. Using lightweight potting soil rather than saturated topsoil will help reduce the load.

"I cannot think of any downside to vertical gardening except not all vegetables are suitable for growing tall up supports — lettuce, cabbage peppers, eggplant for example," Mr. Fell says. "But they can be used as an edging below the vining plants.

"By extending your (planting) bed away from a wall like an apron, you can have the best of both worlds — climbing vegetables at the back and compact, low-growing vegetables at the front."

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