Guide to Asian greens
The most familiar of the greens, such as bok choy, are now sold in supermarkets, but farmers' markets and Asian groceries offer a wonderful range.
Small, curvaceous, jade-green heads (4–10 in.) with mellow flavor.
Several forms, with a mild to pungent mustard bite and jade-green leaves and stems ― some broad, smooth, and succulent with ruffled leaves, others thin with smoother leaves.
Dark green leaves top smooth, ivory stalks with a crisp, juicy texture and a mild, slightly cabbage-like flavor. Most supermarkets carry the mature sizes (up to 20 in.). Shorter heads (6–8 in.) are found mostly in Asian markets.
Bright green, slender, fleshy, leafy stalks with tiny yellow buds or flowers have an earthy, slightly bitter mustard flavor. Young ones are often labeled choy sum.
Literally, choy sum means "the heart of the vegetable," but this confusing name can refer to several things, including both yao choy or a miniature bok choy with yellow flowers.