Is the wild walnut actually a walnut? Let's make it clear once and for all
The wild walnut is a type of walnut, also known as mountain walnut, hickory, autumn peach, etc. It is a deciduous tree or small tree of the genus Juglans in the family Juglandaceae. Its main difference from other species in the same genus is that after the leaflets mature, the underside is densely covered with short pubescence and stellate hairs, the infructescence is long and drooping, and the seed oil content reaches 34%. It is edible, can be used to make soap, and serves as a lubricant. The wood, bark, and fruit peel have many economic and medicinal uses, and it is often used as a rootstock for edible walnuts.
The wild walnut tree reaches 12-25 m in height and 1-1.5 m in diameter at breast height. The young branches are grayish green, covered with glandular hairs, and the pith is separated into thin plates. The terminal bud is conical and exposed. The odd-pinnate compound leaves are usually 40-50 cm long, with both the petiole and rachis covered with hairs, and have 9-17 leaflets. The leaflets are nearly opposite, sessile, hard papery, ovate-oblong or long ovate, 8-15 cm long and 3-7.5 cm wide, with acuminate tips, oblique rounded or slightly oblique cordate bases, and finely serrate margins. Both surfaces have stellate hairs, sparse above and dense below, and the midvein and lateral veins also have glandular hairs, with 11-17 pairs of lateral veins.
The male catkins of the wild walnut grow in the leaf scar axils at the tips of the previous year's branches, and the inflorescence axis has sparse hairs. The male flowers have glandular hairs, about 13 stamens, yellow anthers, and a slightly protruding connective. The female inflorescence is erect, growing at the tip of the current year's branches, and the inflorescence axis is densely covered with brown hairs, with the female flowers arranged in spikes. The female flowers are densely covered with brown glandular hairs, the ovary is ovate, and the style is short. The infructescence usually has 6-10 fruits or only a few due to female flower infertility. The fruit is ovate or ovate-round, the exocarp is densely covered with glandular hairs, and the endocarp is hard, with irregularly arranged sharp spiny protrusions and depressions between the ridges. The flowering period is April-May, and the fruiting period is August-October.
The wild walnut grows in mixed forests at an altitude of 800-2000 m. Its natural habitats are mostly in warmer zones. It is a warmth-loving tree species, but it is highly cold-resistant and not tolerant of damp heat. It requires sufficient sunlight and has relatively high demands for soil fertility. It is not tolerant of barren soil and prefers fertile, moist, well-drained slightly acidic to slightly alkaline soil. Its producing areas are distributed in Gansu, Shaanxi, Shanxi, Henan, Hubei, Hunan, Sichuan, Guizhou, Yunnan, Guangxi, Xinjiang, and other places.
The seed oil of the wild walnut is edible, can be used to make soap, and serves as a lubricant. The wood is solid and does not crack over time, and can be used for various kinds of furniture. The bark and exocarp contain tannins and can be used as raw material for tannin extract. The endocarp is thick and can be used to make activated carbon. The phloem fibers of the bark can be used as raw material for the fiber industry. Wild walnut oil has the effects of moistening the intestines and relieving constipation, killing insects, and astringing sores. Wild walnut kernel has the effects of moistening the lungs and resolving phlegm, warming the kidneys and supporting yang, moisturizing the skin, and relieving constipation.