Brassica rapa subsp. chinensis.

The classic pak choi in its mature, fully developed form — the version found by the thousand in Cantonese markets and which has structured the everyday cuisine of southern China for more than two thousand years. The name pak choi (sometimes spelled bok choy) comes from Cantonese 白菜 (baak choi), literally "white vegetable," in reference to its broad, fleshy white stalks. A linguistic curiosity: in Mandarin, this same term báicài actually designates napa cabbage, and our pak choi is called xiǎo báicài there ("little white cabbage"). This drift between the Chinese languages testifies to a very ancient domestication — the first Chinese agricultural treatises mention it as early as the 6th century AD, in the famous Qimin Yaoshu. Botanically, it's the same species as the turnip and rapini: Brassica rapa, with its multiple subspecies arising from a millennium of selection practiced in northern China.

An open vase-shaped plant, 25 to 35 cm tall at full maturity, forming a crown of broad, fleshy, crunchy white petioles topped by rounded dark green leaves, glossy and lightly curled. Different from the baby pak choi already described in our pages, where the whole plant is harvested at just 30 days for tender mouthfuls — here, it's the mature version cooked by separating the two parts, because they have distinct cooking times. The white stems, juicy and crunchy (mild flavour, lightly sweet, recalling napa cabbage but finer), are stir-fried first in the wok with garlic, ginger and sesame oil; the green leaves, more delicate, are added at the end to stay tender and bright green.

Present in all the Cantonese classics — stir-fried with beef and oyster sauce, in a bowl of wonton noodles, in hot pot, in dumpling soup, or simply steamed and drizzled with a reduction of soy sauce, sesame oil and fried garlic. Note: the white stems contrast beautifully in the dish.

Grower's tip: Like all Brassica rapa, pak choi hates heat and bolts quickly under a summer heat wave. Winning Québec strategy: sow at both ends of the season — mid-April to mid-May for the spring harvest, then early August to early September for the fall harvest (often the most generous, the leaves becoming especially tender and sweet under cool nights). Direct-sowing is preferable; pak choi doesn't like being moved. Harvest by cutting the whole plant at the base, or pick outer leaves as needed and let the heart keep growing. Like all cabbages, susceptible to the cabbage worm and cabbage fly — insect netting from sowing recommended.

• Open-pollinated. Annual. Insect-pollinated; crosses with other Brassica rapa (turnip, rapini, mizuna, napa cabbage) — isolate rigorously for seed saving.
• Height: 25 to 35 cm.
• Maturity: 45 to 60 days.
• Exposure: full sun in spring and fall; part shade mandatory in summer.
• Rich, fresh, well-drained, slightly alkaline soil. Space plants 20 to 25 cm apart.
• Direct-sow mid-April to mid-May for the spring harvest, then early August to early September for the fall harvest. Tolerates light frosts.