What to do now
Mildest step first.
- Cut plants with a short stalk and no open flowers now, and use the leaves soon.
- Pull plants that are already flowering.
- Plan a fall crop: sow about 11 weeks before your first fall frost, under row cover.
- For another spring try, keep seedlings above 50°F at night and grow a slow-bolting variety.
Not sure this is it? Check other napa cabbage problems
Is it bolting?
A bolting napa cabbage stops folding its leaves into a head. A firm stalk pushes up through the center, the plant grows taller and looser, and small yellow four-petaled flowers follow within a week or two. If you are not sure, cut one plant in half: a stalk in the middle, rather than tightly packed leaves, means it has bolted. Once that stalk starts, the plant does not go back to heading.
Cold nights, then long days
The trigger usually comes weeks before you see it. Clemson Cooperative Extension notes that Chinese cabbage can bolt after 10 or more days in a row between 35 and 50°F following a period of good growth, and Johnny's Selected Seeds warns that young plants may bolt after frost or more than a week of nights below 50°F. A spring crop set out early meets exactly those nights, then grows into the long, warm days of late spring, which push the stalk up fast. A fall crop grows into shorter, cooler days instead, which is why fall napa usually heads well and spring napa often does not.
Loose plants that never head
Some plants neither bolt nor head; they stay a loose, open rosette. The usual causes are heat, a sowing made too late for the head to fill before cold weather, crowding, and uneven water or too little nitrogen. Clemson puts napa's best growing temperatures at 60 to 65°F. Give each plant 12 to 18 inches (Clemson suggests 18 inches for napa types), water about an inch a week and more in hot spells, and with nitrogen three to four weeks after transplanting or . Flea beetles and cabbage worms can stall young plants too; laid on the day you sow keeps most of them off.
What to do now
A plant with a short stalk and no open flowers is still worth eating. Cut it now and use the leaves within a few days, cooked or in a fresh geotjeori, before they turn tough and sharp. Plants already in flower are best pulled. Use the bed for a summer crop from another family, and sow napa for fall in a bed that did not grow cabbage-family crops this year, which helps keep clubroot and black rot from building up.
Next time
For a dependable crop, grow napa in fall. Sow about 11 weeks before your first fall frost, in the bed or in cell trays to transplant 3 to 5 weeks later with the root ball intact. If daytime highs are still above about 90°F on your sowing date, sow a week or two later; mature heads hold through light frosts. If you want a spring crop anyway, choose a variety sold as slow-bolting, keep seedlings warm indoors, and set them out only once nights stay above 50°F. Even then, some plants may bolt.
Growing it again? When to plant napa cabbage for your ZIP code
- When should I plant napa cabbage and Korean radish for fall kimchi?Sow napa cabbage about 11 weeks before your first fall frost and Korean radish (mu) about 10 weeks before it. Both grow best into cooling fall weather, hold through light frosts, and should be harvested before the first hard freeze.
- Why did my broccoli skip making a head and go straight to flowers?Broccoli bolts when it experiences heat or stress during head formation — once it starts flowering, the head is unsalvageable, but timing adjustments can prevent it next season.
- Why is my spinach bolting?Spinach bolts when spring days get long, and warm weather speeds it up. Once a center stalk rises, harvest the whole planting. Next time sow earlier, choose slow-bolting varieties, or grow it in fall.