Brassica rapa subsp. chinensis var. rosularis Seeds | Rosette Cabbage
LATIN NAME: Brassica rapa subsp. Chinensis var. Rosularis
COMMON NAME: Tai Ko Tsoi
Plant Profile
Tai Ko Tsoi is a rosette-form Chinese brassica, grown for spoon-shaped, dark green leaves that sit in a neat flat rosette rather than hearting. Plants are small, 20-25 cm across, and can be cut leaf by leaf or taken whole within 30-40 days of sowing.
The leaf stalks are pale green and thick, the blades are smooth and slightly waxy, and the flavour is mild with a faint mustard note that sweetens after frost. It is one of the quickest crops in the catalogue and one of the few that will produce a cut in a short autumn gap.
The variety belongs to Brassica rapa, the turnip and pak choi group, and it is grown across southern China as a cool-season green. Rosette types like this one are more cold-tolerant than the hearting pak chois and are often overwintered under cover.
Science & Biotechnology
Brassica rapa and Brassica oleracea split from a common ancestor and have been domesticated into sharply different crops: turnips, pak choi, mizuna and this rosette green on one side; cabbage, broccoli and kale on the other. The leafy types were selected for rapid growth and low fibre rather than for storage heads.
The mild mustard flavour comes from glucosinolates, chiefly gluconapin, which break down into isothiocyanates when the leaf is cut or chewed. Cool weather and a touch of frost reduce the pungency, which is why autumn-grown leaves taste sweeter than summer ones.
Rosette habit is a matter of internode length: the plant keeps its stem short, so the leaves emerge in a flat circle instead of climbing. That is what allows a dense planting and a cut-and-come-again harvest, and it is the reason the crop is popular in market gardens.
Uses & Benefits
In the kitchen the leaves go into stir-fries, soups and noodle dishes, and the stalks need a minute longer than the blades. The whole rosette can be blanched and dressed, or used as a wrapper for dumplings. It is a good substitute for pak choi in any recipe, with a slightly firmer texture.
In the garden it is a gap-filler: sown after early potatoes, after broad beans, or between slower brassicas, it produces a cut in five weeks. It also works in a container, and it tolerates light shade. Commercially it is a specialist market-garden crop, sold in bunches at Asian markets and increasingly at farmers markets.
Growing from Seed
Sow from March to September at 15-20°C, 1 cm deep, in modules or direct. Germination in five to ten days. For a continuous supply, sow a short row every three weeks rather than a large one at once, since the plants bolt quickly in heat.
Plant out at 20 cm apart in full sun or light shade, in soil that holds moisture and has plenty of organic matter. Water regularly: dry spells make the leaves tough and encourage bolting. Net against flea beetle when the seedlings are small, and harvest whole rosettes or outer leaves while they are still young. In autumn, a cloche will carry the row through light frost.
Our Take
Five weeks from seed to plate, and one of the few greens that tastes better after a cold night. The best gap-filler in the catalogue.
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