Asian mustard (Brassica rapa rosularis) having a rosette of edible dark green spoon-shaped glossy leaves also : the leaves.
Sow tatsoi in spring and again in late summer for harvest in fall. Sow in double rows, with rows spaced 10 inches (25 cm) apart. Plant seeds 2 inches (5 cm) apart and barely cover them with soil. Gradually thin to 8 inches (20 cm) apart.
Tatsoi is a very versatile green, equally suited to being served raw or lightly cooked. To make it easy, just use tatsoi anywhere you'd use spinach. Lightly steam or sauté it, wilt the leaves with a warm dressing, or add them to a soup at the end of cooking.