Bio Japanese Greens Tatsoi - Brassica Narinosa. Sow under glass from March to May. Sow outdoors from May to August. Plant out after emergence. Tatsoi is a variety of the well-known pak choi. It is a Chinese leaf vegetable which, like pak choi, is part of the cabbage family and has a mildly spicy cabbage flavour.Annual. Organically grown seeds. Enough seeds to sow: 1 mÂ².