(MONEY Magazine) – If this spring your fancy is turning to tomato seeds and trowels, join the club. According to a recent Gallup survey, gardening now shares top billing with swimming and walking as one of the three most popular hobbies in America, with 71% of households spending a record $22.4 billion on gardening supplies last year. But green thumbs aren't just getting bigger. They're also getting smarter: A record 40 million home gardeners enlisted landscape professionals to help them plan their patches last year, up 35% from 1992.

A poorly designed landscape, reports a recent study by the Journal of Environmental Horticulture, can actually decrease the value of your home by 10%. By contrast, a bit of well-planned Eden can boost your house's price at resale by as much as 5%. To grow the most value, say the dozen garden designers, landscape architects, nursery owners and horticulturists we consulted, you must position your garden in the most favorable spot and cultivate plants appropriate to your climate and region. "Otherwise, it's the equivalent of painting your house bright pink," says Mike McGrath, editor-in-chief of Organic Gardening magazine. Carefully mapped greenery can frame scenic views, hide unsightly ones and even save you money. Notes Dick Campbell, a nursery owner in Lincoln, Neb., "Planting a leafy tree or shrub that will cast shade on an air- conditioning unit can lower your electricity costs"--by up to 10% a month. And installing only 600 square feet of easy-care tomatoes, carrots or lettuce alongside your favorite posies can slice $300 or so off your grocery bills.

A professional garden plan typically costs a few hundred dollars before you so much as hoist a shovel, but that can be a small price to pay. "If your garden becomes an eyesore because you've put in plants with no advance planning, it can cost thousands of dollars to dig them out and start over," says Don Williams, a garden designer in Tequesta, Fla. Nor should you forgo an attractive plan because you lack the time and money to implement it all at once. Any good landscape planner can sketch a logical structure for your garden that's flexible enough to be filled in gradually. For instance, in Year One, you might dig in walkways, shade trees and shrubs; in Year Two, large flowers, bulbs and perennials, such as peonies and irises; in Year Three, smaller plants, vegetables and annuals, such as marigolds and snapdragons. Here's how to get the right plan and planner for your yard:

Make a list of the plants and flowers you like that will grow well in your area. Hardy native species such as those in the Chadds Ford, Pa. garden pictured above will be less expensive than exotic imports that have been genetically altered to tolerate your climate. They're also easier to maintain-great news for weekend gardeners. That means Minnesotans should favor daylilies, not flowering dogwoods; Arizonans, barrel cacti, not hostas. To learn more, you might quiz neighbors whose gardens you admire, horticulturists at nearby public gardens and exhibitors at the big annual flower shows held in 31 cities across the country, usually in March. For example, the Philadelphia Flower Show, at 166 years the country's oldest such gathering, boasts 56 different garden layouts and several hundred new plants on six acres. It runs from March 5 through 12 ($12.50 admission for adults; 215-625-8253).

If you haven't done much gardening, hire a landscape designer. The typical designer charges $200 to $300 to create a one-time comprehensive plan for your site. That plan should include everything you want to incorporate, including the exact proposed location and names of all trees, shrubs, plants and any additional elements, such as fountains or walkways. But be forewarned: No official licensing is required, so "anyone can call himself a garden designer," says Jerry Somalski, himself an experienced designer in Essexville, Mich. To find an accomplished landscape designer, ask for referrals from friends, established nurseries and design or architectural firms in your area. Then make sure you interview at least two candidates and visit some of their clients' completed gardens before signing any contracts.

If you plan any construction, hire a landscape architect. Most garden designers can site a lily pond or a terrace, but if your project includes earth-moving construction such as putting in a driveway, building a pool or installing a gazebo, you'll need a landscape architect. To qualify, the 30,000 landscape architects in this country must have acquired a three- to five-year professional degree, passed a tough national exam and, in everywhere except Alaska, Colorado, New Hampshire, North Dakota and Vermont and Washington, D.C., completed a rigorous licensing program. Landscape architects usually charge $75 to $150 an hour to draw up a detailed plan, which could run a total of $4,000. For a referral, call local nurseries, your chamber of commerce or the American Society of Landscape Architects (202-686-2752). Check references as you would for a garden designer.

If you're a veteran gardener, draw your own plan. First, walk around your yard and take detailed notes. Are there unsightly views to hide? Are some worthy plants hidden in overgrown areas? Any sad-looking bare spots? To make plant placement easier, try the Yard & Garden Remodeling Kit (free at most nurseries and garden centers), which lets you shuffle miniature trees, shrubs and flowers on a rough grid that you draw of your property. Some principles to remember:

Note where and for how long sunlight hits each day. For example, ray-loving roses won't thrive under an elm tree, while delicate impatiens need shade.

It's okay to mix flowers, herbs and vegetables in the same plot. "You'll add color and variety," says Somalski.

Consider natural-looking designs (like the one pictured on the previous page). "It will be easier to maintain than a precisely sculptured bed," says Tina Houghton, a landscape designer in Tulsa.

Once you've got the plan you want, the only trick left is to execute it. Homeowners who do the work themselves should count on spending $2,000 or so on materials for the typical 1,500-square-foot flower garden in a quarter-acre yard. Or you can follow the lead of William and Avis Biggerstaff, ages 69 and 66, respectively. Not only did they ask Houghton to design an ornamental 1,400-square-foot flower garden last year around their new home in Tulsa (plan cost: $300), they agreed to another $4,000 to have her implement it. Says William: "It was comforting to have someone we trusted do it all for us."