苦麻菜 (Mand: kǔ má cài; Cant: fu2 maa4 coi2)
Bitter Hemp
This, I'm told, a variety of lettuce, grown mainly in Yunnan province. It grows to around 50cm long (The ones in the image were around 40cm). It was originally used as animal fodder, but the locals developed a taste for its bitter flavour and from there it spread.
The leaves are briefly blanched in boiling water, then refreshed in cold water to remove some of the bitterness, then stir fried or added to soups etc.
Although it can be more bitter when older, younger leaves, while bitter are not unpleasantly so. This is one I like.