Juglans mandshurica Seeds | Manchurian Walnut
LATIN NAME: Juglans mandshurica
COMMON NAME: Manchurian Walnut
Plant Profile
Juglans mandshurica is the walnut of the north-east, and it is grown for timber and for a shell that is almost impossible to open. The tree reaches twenty-five metres with a straight trunk and a broad crown, and the leaves are among the largest of any walnut, up to a metre long with nine to seventeen leaflets. The young leaves and shoots are covered in a sticky, rusty down.
The fruit is a green husk holding a thick, deeply ridged shell, and the kernel inside is small and hard to extract. The species grows in mixed forest with Korean pine and with linden, on deep, moist soils, and it is hardy to about minus thirty-five, which makes it the walnut for cold continental climates.
Science & Biotechnology
The genus produces juglone, a naphthoquinone that is toxic to many plants and that leaches from the roots, the leaves and the husks. It is why little grows under a walnut and why the husks were used to kill fish and to treat ringworm. The concentration in J. mandshurica is high, and the fallen leaves suppress competition on the forest floor.
The timber is the other reason for the tree. The wood is hard, dark, straight-grained and takes a fine polish, and it is used for furniture, for veneer and for rifle stocks. It is one of the most valuable hardwoods of north-east Asia, and the species has been heavily logged, so old trees are now scarce across its range.
Uses & Benefits
The kernel is eaten in China and in Korea, usually roasted, and it is pressed for an oil used in cooking and in lamps. The husk is used for dyeing and for tanning, and the shell is burned for a dark pigment used in ink. The tree is also grown as a rootstock for the common walnut in cold climates, since it is hardier than the English walnut.
In Chinese medicine the kernel and the bark are used for a range of complaints, and the green husk is applied to skin infections. The timber is the main commercial product, and the tree is planted in shelterbelts and in mixed forest for its timber value.
Growing from Seed
Walnut germination is slow and depends on the shell weathering. Sow the nuts in autumn, in a pot or in a nursery bed, and leave them outdoors through winter; the husk should be removed first, since it inhibits germination. Mice and squirrels take a share, so cover the bed with mesh.
The tree wants deep, moist, well-drained soil and full sun, and it grows fast while young. Plant it where the roots have room, since the taproot is long and the tree resents transplanting after two years. Keep it away from a vegetable garden and from a patio, because the juglone in the leaves and roots will suppress tomatoes, potatoes and most shrubs within the spread of the canopy.
Our Take
A cold-hardy walnut for timber and for a difficult nut, and a tree to plant where its juglone will not trouble the rest of the garden.
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