Napa cabbage (Brassica rapa subsp. pekinensis), also called Chinese cabbage, is a brassica native to East Asia, related to turnips and bok choy more closely than to the round-headed cabbages most Kentucky gardeners already grow. It forms a dense, elongated, barrel-shaped head of crinkled, pale green leaves wrapped around wide, crisp white ribs, prized for its mild, sweet flavor in stir-fries, soups, and kimchi. The plant is a cool-season annual that bolts and turns bitter quickly once summer heat sets in, so success in Kentucky depends more on timing than on technique. Growing napa cabbage is straightforward for anyone who has grown lettuce or regular cabbage, provided the crop is planted to mature in cool weather rather than pushed through a hot summer.
Sowing and planting
Napa cabbage can be direct-sown or started as transplants, but in zone 6b it performs best as a fall crop rather than a spring one. Spring-sown napa cabbage almost always bolts once the weather turns warm, sending up a bitter flower stalk before the head has filled out, so most Kentucky gardeners skip spring planting altogether and aim for a late-summer sowing timed to mature in the cooler, shorter days of autumn. Start seed indoors in mid-to-late July, about 4 to 5 weeks before transplanting, or direct-sow in the garden in early-to-mid August once the worst of the summer heat has started to break.
Sow seed about 1/2 inch (1 cm) deep, and thin or transplant seedlings to a final spacing of 12 inches (30 cm), with 18 to 24 inches (45 to 60 cm) between rows to give the heads room to fill out. Choose a bed in full sun for the fastest, firmest heads, though a little afternoon shade helps keep soil temperatures down during the final warm weeks of late summer. Work compost into the bed before planting, since napa cabbage grows quickly and draws heavily on soil fertility in its short season.
A loose, well-drained soil with a near-neutral pH suits napa cabbage best; heavy, compacted clay slows root development and can leave heads lopsided or loosely wrapped. If starting seed indoors, use a seed-starting mix rather than garden soil, and transplant seedlings out as soon as they have three or four true leaves, since root-bound transplants are slow to resume growth and lose some of the head-forming time the fall window allows.
Growing on
Keep the soil evenly moist throughout the growing season; napa cabbage has a shallow root system and wilts quickly in dry soil, and inconsistent watering is a common cause of heads that split or fail to fill out properly. A couple inches of mulch around the plants helps conserve moisture and keeps soil temperatures down while the crop is still establishing in late-summer heat. Feed with a balanced fertilizer at planting, then side-dress with a nitrogen-rich feed three to four weeks later once heads begin to form, since the plant needs strong, steady leaf growth to build a full head before cool weather sets in.
Weed carefully while plants are small, since napa cabbage's shallow roots are easily disturbed by aggressive cultivation; shallow hoeing or hand-pulling works better than deep tilling between plants. Watch the crop closely as days shorten in September and October: growth slows as temperatures drop, but a light frost does the plant no harm and actually improves the flavor of the heads.
Harvesting
Napa cabbage is ready in about 70 days from sowing, though heads can be picked a little early if space is tight or left a little longer for size, as long as hard freezes are still weeks away. Harvest when a head feels firm and dense when squeezed, rather than loose or puffy. Cut the head at the base with a sharp knife, leaving the outer wrapper leaves in the bed if they're still intact and usable.
Heads tolerate a light frost well and often taste sweeter afterward, but a hard freeze damages the outer leaves and can ruin the head, so plan to have the crop in before the first hard freeze typically arrives in Kentucky, usually mid-to-late October. Harvested heads keep for several weeks in a refrigerator or root cellar wrapped loosely in plastic, and the crop also stores well shredded and fermented into kimchi for longer-term use.
Problems and pests
Ragged holes chewed through the leaves
Cabbage worms and cabbage loopers, the larvae of white butterflies and brown moths, chew large irregular holes in the leaves and can skeletonize young plants if left unchecked. Handpick caterpillars when you spot them, and treat with Bacillus thuringiensis (Bt) if the infestation is heavy; a floating row cover placed over the bed at planting keeps the egg-laying adults off the crop entirely.
Small shot-holes in young seedlings
Flea beetles riddle young leaves with tiny holes, and damage is worst on seedlings just after transplanting or emergence. Established plants usually outgrow the damage, but a heavy early infestation can stunt or kill small seedlings. A floating row cover over newly planted beds is the most reliable protection until plants are large enough to shrug off the feeding.
Plant bolts and sends up a flower stalk instead of heading
Bolting happens when the plant is exposed to a stretch of warm weather, especially in spring plantings or an unusually warm late summer. Once a plant bolts, the head won't fill out properly and the leaves turn bitter. There's no fix once it starts; avoid it by sticking to a fall planting schedule and choosing a bolt-resistant variety if a summer sowing is unavoidable.
Wilting, stunted plants with swollen, distorted roots
Clubroot, a soil-borne fungus-like organism, distorts roots into galls that choke off water and nutrient uptake, leaving plants wilted and stunted even in moist soil. It persists in soil for years, so the main defenses are prevention: rotate brassicas onto a four-year cycle, keep soil pH above 7.0 if clubroot has appeared before, and avoid bringing in soil or transplants from infected ground.
Clusters of small insects on the undersides of leaves
Aphids cluster on new growth and leaf undersides, sucking sap and leaving behind sticky honeydew that can lead to sooty mold. Light infestations wash off with a strong jet of water; heavier infestations respond to insecticidal soap. Encouraging ladybugs and other beneficial insects in the garden keeps aphid populations in check over time.
Varieties worth growing
- Michihili – A tall, upright, cylindrical heading type with a long tradition in Chinese cooking; matures a bit slower than rounder types but stores well.
- Minuet – A compact, early-maturing variety well suited to Kentucky's shorter fall growing window, with good bolt resistance.
- Bilko – A reliable, widely grown hybrid with dense, barrel-shaped heads and strong disease resistance.
- Rubicon – Fast-maturing and vigorous, producing large, heavy heads with good tip-burn resistance.
- Tenderheart – Known for sweet, tender interior leaves and a head that holds well in the garden without splitting.