The male flowers are in drooping catkins 9–40 cm (3+1⁄2–15+1⁄2 in) long, the wind-pollinated female flowers (April–May) are terminal, in spikes of 4 to 10, ripening in August–October into nuts, 3–7.5 by 3–5 cm (1–3 by 1–2 in), with densely glandular pubescent green husk and very thick shell.

[citation needed] The Manchurian walnut contains and exudes much lesser quantities of allelopathic compounds (such as juglone) than other popular Juglans species[4][better source needed] and usually causes few significant allelopathic effects in cultivation.

[5][6] Juglans cathayensis, characterized by tomentose leaflets, producing more flowers per spike and growing south of the Yellow River, was sometimes recognized as a species separate from J.

[citation needed] The Japanese walnut is listed by some authorities as Juglans mandshurica var.

The tree is exceptionally hardy (down to at least −45 °C), has a relatively short vegetation period compared to other walnuts, grows rapidly and is cultivated as an ornamental in colder temperate regions all over the Northern Hemisphere.