Walnut trees

Juglans regia (English walnut) and Juglans ailanthifolia (Japanese walnut) are large deciduous trees from the Juglandaceae family. Botanically, they are monoecious, wind-pollinated, with odd-pinnate leaves. While J. regia has fruits (false drupes) with a typical lobed kernel, J. ailanthifolia (especially var. cordiformis) produces fruits in clusters, often heart-shaped with a smoother shell. Both species secrete the allelopathic substance juglone into the soil, which suppresses the growth of surrounding vegetation. Nutritionally, the fruits are energy-rich due to their high fat content. J. regia is unique in its record-breaking content of plant omega-3 (alpha-linolenic acid). They are also an important source of protein, magnesium, phosphorus, and B vitamins. The phytochemical profile is defined by the presence of the naphthoquinone juglone and a high concentration of polyphenols (especially ellagitannins in the thin skin of the kernel). These have strong antioxidant and anti-inflammatory effects, and J. regia also contains biologically significant amounts of melatonin.