Zanthoxylum ailanthoides aka Japanese Prickly Ash

Zanthoxylum ailanthoides is a tree in the rue family, Rutaceae. Its native range spans southern China, eastern Asia, and the Philippines. It also grows in Japan, Korea, and Taiwan. Wild plants grow in mountains, upland thickets, and lowland forests. It occurs in warm temperate and subtropical regions. Its range reaches the tropics in the northern Philippines.

Sources give a height of about 59 feet [18 metres]. Useful Tropical Plants also reports trees reaching 82 feet [25 metres]. The sources disagree on whether it keeps its leaves. Plants For A Future calls it deciduous. Useful Tropical Plants describes it as apparently evergreen. Flowers grow on wood formed in past years. Male and female flowers grow on separate trees. Insects pollinate them, and a lone tree cannot fertilise itself. Grow both sexes if you need seed. The small fruits grow in clusters, each holding one seed.

This tree prefers deep soil that holds moisture but drains well. It can grow in sand, loam, or clay. It accepts mildly acid, neutral, and mildly alkaline soils. Give it full sun or a place with some shade. Plants For A Future lists USDA zones 8–11. Both main care sources describe it as prone to frost damage. In Britain, it grows outdoors only in the mildest areas. Suggested garden settings include woodland canopy plantings and sunny woodland edges.

People cook the seeds and use them as a hot spice. They can serve in place of red pepper. The fruit clusters make the seeds easier to gather. Sources also list young leaves as edible, without giving preparation details. People gather wild trees for local food, medicine, and timber. Traditional medicine uses resin from the bark and root bark. Reported uses include easing coughs and gas, and as a stimulant. These reports do not establish medical safety or benefit. The sources list no known hazards, but give no detailed safety assessment.

Fresh seed is best sown under glass in autumn. Stored seed may need three months of cold treatment. It can take another year to sprout after the first spring. Keep seedlings in a cold frame through their first winter. Plant them out in early summer. Other methods include summer cuttings, root cuttings, and late-winter sucker removal.