Apple trees grown in Minnesota have the same requirements as those grown in other places: full sun, well-drained soil, a temperate climate that permits dormancy and fulfills the buds’ chilling requirement to break dormancy, and adequate soil moisture, whether from rainfall or irrigation. In addition, apple trees benefit from being planted on slopes, so that cold air can drain away downhill, while warmer air floats back uphill.
In Minnesota, the importance of planting on a slope and not in a low spot cannot be overemphasized. Cold air really does sink into low spots, and apple trees must be sited so that the cold air can drain away from them. Otherwise, flowers and tiny fruits can be ruined by spring frosts. South-facing slopes are to be avoided, because these sites warm up significantly earlier in spring, and trees planted on these slopes will tend to flower much earlier than those planted elsewhere. Early bloom is of no benefit. It increases the chance that the flowers will be killed by frost and the crop lost.
Rows should be oriented north-south wherever possible for best light interception, leading to superior fruit quality. If ground is so steep that north-south rows may lead to erosion problems, the land may be too steep to be part of a commercial orchard planting. Any orientation across a slope will require driving equipment across the slope, which can be quite dangerous if the ground is steep.
Supplemental irrigation is particularly helpful in the first year or two after planting. Normal Minnesota weather usually brings enough rain during the growing season for trees to grow and produce good fruit, but on sandy soils, irrigation for the life of the planting may be essential. Even on moisture-retentive soils, irrigation can be very useful during periodic summer dry spells.
Mulch of wood chips or similar materials, applied in the tree row, can also help keep the trees’ root zones cool and moist. Although wood chip mulch will not entirely control weeds, it will suppress them. Growers whose trees are mulched can attend to the few weeds within the rows on a more flexible schedule than growers who maintain an herbicide strip in the rows. Wood chip mulch also affects soil properties and leads to improved tree health and vigor, as well as increased yields.