Yuzu

What it is

Yuzu is about 5–7 cm (2–2.8 in) across, with a thick, bumpy rind and many large seeds inside. The juice is sharply sour. The fruit starts green and changes through yellow towards orange as it ripens.

Green yuzu is a cooking ingredient in its own right. Later fruit yields more juice, while its fragrant peel seasons fish and soups. Both the outside and the inside earn their place in the kitchen.

Where it comes from

Yuzu has a long history in China and Japan. Its family tree brings together mandarins and papedas, another group of citrus. Kochi, on Japan’s island of Shikoku, is the country’s largest yuzu-growing region.

The fruit also grows in California: the Riverside collection received seed gathered in China by plant explorer Frank Meyer in 1918.

How it's eaten where it grows

In Kyushu, green yuzu peel is ground with chilli and salt into yuzugosho, also called yuzu kosho. A little seasons a hot pot, udon, soba or sashimi. In Oita, sugar-glazed yuzu peel accompanies tea or appears among the dishes for New Year.

In Korea, the fruit is called yuja. For yujacha, the fruit is preserved in sugar or honey, then diluted with water to drink. Japanese ponzu uses yuzu juice for its sourness.

How it's grown

Yuzu grows as a thorny evergreen shrub or small tree, with upright branches and fragrant white flowers in spring. In Britain it can be grown in a container in a greenhouse or conservatory. Growers can raise new plants from cuttings taken when the young stems have become partly woody.

When and where you'll find it

At Riverside in California, green yuzu is usually used for cooking in September and October. In Umaji, Kochi, the yellow-fruit harvest usually falls in November.

The flavour travels further than the fresh fruit. Most of the yuzu shipped from Oita goes into processed foods such as juice and yuzu kosho, and Japanese confectionery shops and farmers’ markets there sell sweets made from the peel.