Carefully consider the planting site for black walnut trees, Persian walnut trees grafted onto black walnut stock, or butternut trees if other garden or landscape plants are to be grown within the root zone of the mature nut trees. The toxic zone extends an average of 50 to 60 feet from a mature tree. These plants grown within the root zone of a black walnut or butternut tree usually start to wilt within one to two months after planting, then die, or are severely injured. Antagonism has been observed in several garden plants, notably tomatoes, potatoes, peppers, and eggplant fruit crops such as apple, blackberry, blueberry, and grape and landscape plants such as azalea, rhododendrons, mountain laurel, white birch, cotoneaster, hydrangea, lilac, pines, spruces, and yews. Black Walnut and Butternut Toxicity ProblemsĪ chemical in the roots, leaves, and hulls called juglone (5-hydroxy-alphanapthaquinone) is capable of injuring other plants. Bearing can be improved somewhat by thinning the nuts in heavy-producing years, increasing nitrogen fertilization, irrigation, and providing adequate sunlight. Some nut trees, especially pecan, exhibit alternate bearing, or periods of nut production that alternate every other year. This requires growing different cultivars that overlap in bloom and are also genetically compatible. Some nut tree species such as chestnuts, hazelnuts, pecans, and Persian walnuts, need cross pollination for nuts to develop and mature properly. Hazelnuts can be allowed to grow as a bush form, or pruned to a single stem, as is done with European hazelnuts in commercial production in Oregon. If logs for lumber are desired, particularly black walnut, a clean trunk for at least nine, and preferable 17 feet, should be created by removing side branches when they attain a diameter of two inches. Low branches, dead limbs, and narrow crotch angles of less than 35° can be removed in the winter. Nut trees require little pruning, although good structural shaping in the early years can help them to develop into healthy trees later. Soil test kits are available from Rutgers Cooperative Extension county offices. A soil test can determine if fertilizer is needed the following years. Water thoroughly every one to two weeks during the first summer. Mulch with straw or hay to reduce weeds and conserve soil moisture. Plant bare-root plants in the early spring. Since hazelnuts are more shrub-like, they can be spaced about ten feet apart. Most nut trees are planted 25–30 feet apart. Neutral or slightly acid soils are best suited for nut trees. Drainage is more critical than soil type. Nut trees should be planted in fertile, welldrained soil. If seedling trees are purchased, be sure that they were grown from the best seed obtainable, and expect them to be quite variable in contrast to the grafted trees. Buy trees from a reputable nursery that labels the trees as budded or grafted from a tested cultivar. Planting and cultural requirements for nut production are similar to practices recommended for other ornamental or fruit trees. The planting site-North, Central, or South Jersey-may determine whether or not a "borderline" nut tree species can survive and thrive. Late spring frosts and drought can also be very damaging. "Borderline" nut trees include Persian walnut, Japanese walnut, heartnut, pecan, and almond where harvests will be limited by low winter temperatures, humidity, length of growing season, and growing-degree days. The most successful nut tree species in New Jersey are Chinese chestnut, black walnut, butternut, several species of hickory, and native hazelnut (or filbert). The average annual minimum temperature should not go below -20☏. ClimateĬlimate is most important in determining whether nut trees grow and fruit satisfactorily. However, this publication is intended for the suburban homeowner or hobbyist who can benefit from the ornamental and shade value of the nut trees as well as their nut crops for food when the nuts ripen each autumn. Nut trees can be grown successfully in New Jersey for their edible nut crop, as a lumber resource, for wind and erosion control, and for habitat and food for wildlife.
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