Most fruit trees need 8 hours of sun each day, so a planting site that receives full sun is your first priority. Early morning sun dries dew off the foliage quickly and minimizes diseases; midday and early afternoon sun improves fruit flavor. Plant fruit trees far enough from shade trees to provide adequate light and to minimize root competition. Your site should have good air drainage. Avoid low spots and areas enclosed by buildings or shade trees, where cold air settles, causing trees to suffer from winter cold and spring frost injury.
A north-facing slope or north side of a building is a good site for frost-sensitive crops such as peaches, Japanese plums, sweet cherries, and apricots. The shadow cast by the slope or building in winter keeps the plant cooler, which delays bud development and bloom in spring, while the higher summer sun angle provides enough light during the growing season. Fruit ripening will also be delayed on a north slope. A south-facing slope or wall hastens both bloom and harvest, and requires extra protection from frosts as well as from winter sunscald. In areas with short or frequently cloudy growing seasons, the hardier fruits (apples, pears, tart cherries, and European or American hybrid plums) do better on a south-facing slope or wall, which receives more intense light.
Where summers are very hot and dry, avoid south or southwestern slopes, or give the trees plenty of irrigation. East- and west-facing slopes have intermediate effects. In areas with strong winds, choose a site protected by existing plantings or buildings, or plant a windbreak. Windbreak trees can also serve as border plantings or screens, provide shelter and nesting sites for insect-eating birds, and may lure pest birds away from your fruit trees. In addition to the right amount of sun and air, soil type should be a major consideration in choosing a site. Once you plant a fruit tree, it will remain in the same spot for many years, so it pays to examine and prepare soil carefully before you plant. Even if this means delaying tree planting by a year, you'll gain back that year in increased tree growth and health.
Your Extension Service agent can provide useful soil survey information. Fruit trees need well-drained soil. Avoid low areas where water puddles during rains. If you don't have any well-drained sites, you can install drainage tiles or build raised mounds or beds (6 to 8 inches high and as wide as the mature tree's spread) where you'll plant the trees. To make mounds, mix equal parts soil from other areas of the yard with compost. If you bring in topsoil of a different texture, mix it into your own soil well.
You will also need to build raised beds if your soil is not deep enough for the trees' roots--at least 3 feet of soil for trees on dwarfing rootstocks, and at least 5 feet of soil for standard-size trees. If you think your soil is shallow, dig a hole or use a soil auger to the necessary depth. While digging, look for an abrupt change in soil texture. Watch for soil that suddenly becomes very clayey; this type of soil will restrict water drainage and root growth into the soil below. Although good soil drainage is one of the most important factors for fruit trees, soil texture will influence their growth. Loam soils, clay loams, or sandy loams are better for fruit trees than very sandy or heavy clay soils.
Different fruit tree rootstocks are adapted to different conditions. Some rootstocks tolerate clayey soils well and others withstand sandy soils. In general, peaches, sweet cherries, Japanese plums, and apricots do better in sandy soils; apples, pears, tart cherries, and European plums do better in heavier soils.
Have your soil tested, preferably the season before you intend to plant your trees. If necessary, add lime or sulphur to correct the pH to a range of 5.5 to 7.0, suitable for most trees. Add phosphate or potash fertilizers if phosphorus or potassium levels are low. All fruit plants will be healthier if the soil contains high levels of organic matter, so turning under a green manure crop or two before planting helps a great deal.
Plant nematode-susceptible stone fruits (peaches, plums, cherries, and apricots) where a grass cover crop or lawn grew for the previous 2 years. Two years without broad-leaved plants almost completely eliminates the most troublesome nematodes, root knot, and lesion, as well as verticillium wilt. Nematode- or verticillium-infected fruit trees are stunted and unproductive, and once infected, there is no cure. Many vegetables and small fruits are susceptible to verticillium wilt. Try not to plant fruit trees where susceptible plants have grown in the last 2 years. If you must plant stone fruits where vegetables grew recently, choose an area where corn has grown.
Have the soil tested for nematodes before planting. If high levels of root knot or lesion nematodes are found, plant the ground with a trap crop of marigolds, which will attract nematodes to their roots, the season before planting the fruit trees. Don't bother planting marigolds around the trees once they're set out to get rid of nematodes; you need to get nematode levels down before tree-planting time. Choose a marigold variety proven to be a good trap crop, such as 'Tangerine' or 'Nemagold' blend. Plant them 6 to 7 inches apart so they form a solid stand, and keep them weeded. In early fall, pull up the marigolds--roots included--and destroy them. Then plant a winter rye cover crop for additional protection against nematodes, and till it in early the next spring before planting trees.
Planting fruit trees in a lawn is fine; just remove the sod in a circle 3 or 4 feet out from each fruit tree, and mix some compost or other organic matter into the whole area. If the lawn contained many broad-leaved weeds, test the soil for nematodes and follow the instructions above for planting marigolds. Eliminate any noxious perennial weeds such as quack grass. Remove competitive grasses such as Bermuda or zoysia from the entire area that the fruit trees will ultimately occupy, and replace them with less competitive groundcovers. Do not replace an old fruit tree with the same or a closely related type of fruit. Not only have nematodes and other soil-borne diseases built up, but the roots of certain fruit trees, such as peaches, exude a toxin that inhibits the growth of new peach roots. Don't place new stone fruit trees right next to older ones, to prevent the spread of non-curable diseases such as X-disease or cherry yellows.