土地经营者不愿在许多其他树种内混栽黑核桃(Juglans nigra L),因其他树种可能受到核桃分泌物的影响。这种影响是核桃醌(5-hydroxy-1,4-naphth-oquinone)所引起的,核桃的叶、果壳和根中都发现有核桃醌。Perry(1967)发现,由于氧气抑制的结果,核桃醌使番茄和豆类的叶面呼吸受到限制。某些针叶树种生长在黑核桃附近时,也发现受到损害。 Land managers are reluctant to mix Juglans nigra L with many other tree species, as other species may be affected by walnut secretions. This effect is caused by 5-hydroxy-1,4-naphth-oquinone, which is found in walnut leaves, husks and roots. Perry (1967) found that due to the oxygen inhibition, walnut quinones restrict leaf respiration of tomatoes and pulses. Some conifers also found damaged when they were grown near black walnuts.