Angelica keiskei koidzumi.
This often hard to find plant is native to the Japanese island of Hachijojima and is renowned for its rejuvenating properties.
The stems are edible and the leaves can be used in tea. The stems and leaves are high in vitamin B12, which is rather unusual in plants.
Best planted in a shady position, Ashitaba can grow to around 1.5m in height.