(ARA) - While the past season's beautiful gardens have bloomed and faded into the past, home gardeners should already be planning for next spring and summer. Take a tip from the professionals and start thinking ahead, before the snow flies.

"It's good to begin planning at least 6 months in advance," says Dennis Buettner, principal landscape architect with Buettner and Associates Inc., in Milwaukee. "Fall is the perfect time to prepare beds for spring planting. Winter is a good time for landscape design, material selection and plant research. Dryer spells in summer and fall are good for site construction. It's important to place plant orders before spring and fall digging, to make sure the desired species and sizes are available."

Gardeners tend to choose flowers and plants they like. But success involves more than selecting flowers in your favorite color or fragrance; they also need the right conditions for growth. They have to be hardy enough for your climate, adapted to soil conditions in your yard and aesthetically in harmony with the site. "You need to consider not just aesthetics, but what plants need to grow," Buettner said. Five main variables are important to consider when planning any garden:

• Hardiness requirements.
• Soil conditions.
• Sunlight.
• Special conditions (Will the plants attract animals such as deer, and are the plants salt-tolerant?).
• Aesthetics.

"Climate is an important consideration," Buettner says. "Plants of the South hold a lot of appeal to people in the Midwest, but are just not going to do well in a colder climate."

Buettner suggests using hardiness zones as a starting point for plant selection. The U.S. Department of Agriculture (USDA) publishes a Plant Hardiness Zone Map, based on average annual minimum temperatures in the United States and Canada. The map is available from the USDA, on garden-related Web sites and can also be found in many gardening books. It tells you the coldest temperatures plants have to withstand in different parts of the country. For example, zone 4 includes southern Minnesota, parts of Wisconsin, Iowa and Nebraska. Native flora in this area can tolerate temperatures to 30 below zero.

Next, you should consider soil conditions. If your soil has seasonal extremes of wetness or dryness, plants must be able to tolerate those swings. Loamy, sandy or clay-heavy soil favors different plants, as does the soil's pH level (acidity or alkalinity). Soil pH affects the release of essential elements necessary for growth and vitality. It also controls plants' ability to absorb nutrients. Levels between 6 and 7 are considered ideal. Most plants will not tolerate extreme acidity or alkalinity. To be safe, Buettner urges people to have their soil tested. Many university extension offices offer this service.

You can help condition soil in the fall by applying an organic nitrogen fertilizer like Milorganite, a popular natural product for lawns and gardens. Milorganite is especially good for preparing new flowerbeds, according to Mike Archer, the company's market development and research coordinator.

For mass plantings in new flowerbeds, Archer recommends working into the soil five pounds of organic fertilizer per 100 square feet. "Fall is a good time to do that because, with a slow-release organic nitrogen, the nutrients break down into the soil at the rate the soil needs them."

Plants also need to be selected for the amount of sunlight available. Few plants can adapt from full sun to dense shade. Learn which plants prefer total sun, partial shade or dense shade. Be aware that as gardens mature, they get shadier. One type of plant might be salt-tolerant and thrive in dry, sunny spots, while other varieties prefer wet, shady areas.

Only after understanding hardiness requirements and soil conditions should you consider aesthetics. Buettner advises stepping back, setting aside your own likes and dislikes, and letting yourself by guided by the style of your home.

"Some architectural styles lend themselves to more elaborate and formal gardens while others may lend themselves to prairie gardens. To enhance the real estate value, the architecture of the building should really set the style of the garden," Buettner stresses.

Careful fall planning and preparation are vital to lush gardens next year. The best advice a seasoned landscape architect can give is this: "Take it slow and do it right."