Walnut may be planted in pure or mixed species stands. There is a tendency to plant pure stands to maximize tree value and simplify planting and management, but over the life of a plantation, unexpected pest or environmental problems could damage a high percentage of trees. For example, unusually cold winter temperatures recently damaged or killed many walnuts in southeastern Minnesota. Mixed stands reduce such risks, have more aesthetic appeal, support a wider variety of plants and animals, and may have less expensive seedling costs.
When white pines are mixed with walnuts, the pines help control weeds by shading the ground, and they improve walnut stem form. Walnuts also can be mixed with hardwood trees that have a similar growth rate, such as red oak and white or green ash. Nitrogen-fixing shrubs, notably autumn olive, can stimulate growth of walnut trees. Different tree species may be planted in alternate rows or mixed within a row; pines often are planted in two out of every three rows.
Black walnut is one of the Midwest's most valuable tree species based on price per board foot. It has long been in high demand throughout the world for wood products because of its beautiful color, strength, durability, dimensional stability after drying, and excellent machining qualities. Besides wood products, walnut trees produce edible nuts, wildlife food, and beauty, while protecting soil and water resources. When you plant and care for black walnut trees, you are making an investment that may pay off handsomely in future years.
As a landscape tree, walnut provides light shade and bright yellow fall foliage, although its nuts can be a nuisance in some landscape settings. A chemical found in the tree's roots, leaves, trunk, and nut husks can inhibit the growth of tomatoes, potatoes, alfalfa, blackberry, domestic grape, lilac, hydrangea, chrysanthemum, paper birch, red (Norway) pine, Scotch pine, hackberry, basswood, apple, and other plants grown too close to a walnut tree. This effect remains long after a walnut tree has been removed.
When Trees start out in the wild, their life begins in an area where that type of tree is adapted to and tolerant of the conditions of that particular site. As the trees mature, the site conditions may change. People may modify the land by building houses or office buildings. The building of these structures most times take away an assortment of brush and small plants, thus altering the natural landscape.. Some trees are tolerant of these man made conditions like Oaks and Elms. The types that are not tolerant and cannot adapt only have one choice, and that is too die. (9)
Leave crop stubble for moisture retention, weed suppression, and erosion control. Remove excess stubble that will interfere with machine planting of walnuts. Chisel-plow the planting site if there is a plow pan, or disk to loosen compacted soil.
Agroforestry generally refers to growing trees at a wide spacing with agricultural crops or shrubs between tree rows or beneath the trees. Trees usually are grown for nuts because wide spacing can lead to poor timber quality. Agricultural crops grown between tree rows provide annual income while nut trees mature. Crops that have been grown with walnut include corn, soybeans, winter wheat, forage, vegetables, berries, and Christmas trees. Over time the nut trees may take over the site and other agricultural activities cease. Agroforest plantations are not easy to manage because the cultivation, harvest, and pest-control activities needed to grow agricultural crops often damage tree roots, stems, or leaves. As a rule of thumb, space trees relatively close together within a tree row (6 to 10 feet), but space rows far apart (40 feet or at least 4 feet wider than the equipment used to maintain annual crops) (Table 1).
Sod strongly competes with walnut trees. Mowing will not adequately control grass. Before planting, remove sod in strips or patches by rototilling, disking, or using herbicides. Clear at least a 7- to 12-square-foot area around each planting spot (1 1/2- to 2-foot radius around each seedling).
To determine the number of trees to plant at other spacings, multiply your proposed spacing in feet within rows by the spacing in feet between rows and divide into 43,560 square feet per acre:
Allow 200 to 300 square feet of growing space around each tree at the time of establishment (Table 1). Gradually thin to about half this density as trees mature. Keep other trees and shrubs from invading. Sod reduces nut production, but also reduces soil erosion and may discourage other plants from invading that would make nut collection difficult.
My trees are doing great! Both plums and peaches are thriving, and a few have reached probably 7 feet tall! I have a couple planted in the yard, but the happiest ones right now are actually living in big black plastic pots on the south side of the house. I think they love the heat there. They seem to be a hearty lot…and I don’t really do anything special for them to keep them thriving. I think if you were to put your baby peach trees outside for the summer, they’d love it, and they’d grow very rapidly. Best of luck!
The timber value of good nut trees usually is low because of their short butt logs, numerous knots, wide growth rings, and high percentage of light-colored sapwood. However, nut plantations can be grown on poorer quality sites than timber plantations.
Forest openings and clearcuts provide an excellent environment for walnut, but brush, broad-leaved weeds, and grasses must be controlled in a 12- to 28-square-foot area around each planting spot (2- to 3-foot radius around each seedling) prior to planting. Plant walnuts where natural regeneration of other desirable tree species is not adequate.