Companion Crop Recommendations for Planting with Black Walnuts

The concept of planting trees in widely spaced rows and growing cash crops in the alleyways is a special form of agroforestry called alley cropping. To be successful, the companion crop’s physiological requirements (i.e., light, water and nutrients) must be accommodated by the tree. Black walnut’s (Juglans nigra L.) foliage and root system are unique and readily adapted to the growth of companion crops. Black walnut is one of the latest species to break dormancy in the spring and is, typically, one of the first to defoliate in the fall. Even with full foliage, it produces a light shade within which many crop species can grow (Garrett et al. 1992). A black walnut’s root system is also uniquely designed leading to reduced competition for soil moisture and nutrients between the species and companion crop. Typically, young walnut produce a deep, penetrating taproot which can extend to more than seven feet in the absence of physical barriers. Its long branch roots are found close to the surface but most of the smaller branch and feeder roots turn down sharply leaving a shallow zone near the soil surface for root development of companion crops. When correctly designed, alley cropping with walnut can be highly profitable. Perhaps the most important decision relative to profitability is the choice of companion crop.