Black walnut

Black walnut is a magnificent tree but demands serious patience and plenty of space. Grafted selections usually start producing after seven to eight years, with full production taking fifteen years or more. The tree produces juglone throughout its leaves, bark, roots, and nut hulls, which leaches into the soil and inhibits many other plants — tomatoes, apples, and blueberries are particularly sensitive. Plan the planting site carefully, as this is a very long-term commitment. The nuts are prized for their intense, distinctive flavour.