What to do now
Mildest step first.
- Find your first fall frost date, then count back 11 weeks for napa and 10 weeks for mu.
- If late-summer heat or flea beetles are a problem, start napa in cell trays and transplant at 3–5 weeks.
- Sow mu directly in the bed; the root is the crop, so it is not transplanted.
- Harvest both before nights drop into the low 20s °F.
Not sure this is it? Check other napa cabbage problems
Kimchi crops want fall
Napa cabbage and Korean radish are that do best as days shorten and nights cool. Johnny's Selected Seeds describes Chinese cabbage as performing best in the gradually decreasing day length and cooler temperatures of late summer, and Clemson Extension recommends sowing it in late summer and fall rather than spring, because young spring plants may after frost or a run of cold nights. Mu behaves much the same way: spring sowings often bolt before the root sizes up, while fall sowings fill out in cool soil and keep well. For a kimjang-sized harvest, fall is the season to plan for.
Count back from your first frost
Count back from your average first fall frost. Sow napa about 11 weeks before it. Most varieties need 60 to 80 days from transplanting, and Johnny's adds 14 to 21 days when you sow directly in the bed. Sow mu directly about 10 weeks before the . Korean types such as Alpine and Summit are listed at about 55 days, and the extra time covers slower growth as days shorten. Where the first frost comes late, the sowing dates move later with it; Clemson's fall transplanting window for Chinese cabbage in South Carolina runs from mid-July in the Piedmont to the end of September on the coast.
Getting through late-summer heat
The hard part is the start. On your sowing date it is often still hot, and flea beetles are at their worst. If daytime highs are still above about 90°F, sow a week or two later; mature heads and roots hold through light frosts, so a short delay costs little. Raising napa in cell trays in light shade and transplanting at 3 to 5 weeks with the root ball intact keeps seedlings out of the bed during the hottest weeks. Cover napa and mu with on the day you sow or transplant, and keep the soil evenly moist so seedlings never stall.
Harvest before a hard freeze
Napa is ready when the head feels firm from top to bottom; mu is ready when the green shoulder is 2 to 3 inches across and the root feels solid. Both handle light frost. A hard freeze is another matter: nights in the low 20s °F can damage napa's outer leaves and lead to rot, and long stretches below about 30°F can leave mu pithy. Watch the forecast and harvest both before the first hard freeze, even if that is earlier than you planned to make kimchi. Johnny's notes that napa heads keep 1 to 2 months near freezing with high humidity and topped Korean radish 6 to 10 weeks at 32°F, though napa salts best within a few days of cutting, while the leaves are crisp.
Garlic, peppers and scallions
The rest of a kimchi garden runs on other clocks. Garlic is planted around your first fall frost, up to about 2 weeks after it, and harvested the next summer. Korean chili peppers for gochugaru are started indoors 8 weeks before your last spring frost and set out 2 weeks after it. Scallions (pa) can be sown about 4 weeks before your in spring and again about 10 weeks before your first fall frost. The kimchi garden calendar on our Korean vegetables page lays these dates out for your ZIP code.
Growing it again? When to plant napa cabbage for your ZIP code
Growing it again? When to plant korean radish for your ZIP code
- Why is my napa cabbage bolting instead of making a head?Napa cabbage tends to bolt when young plants get a frost or a week or more of nights below 50°F, and long, warm days then push the flower stalk up. That is why spring crops fail so often. Use what you can now, and sow the next crop for fall, about 11 weeks before your first fall frost.
- When is Korean radish (mu) ready, and why do roots split or go pithy?Pull mu when the green shoulder is about 2–3 inches across and the root feels firm, usually 55–70 days after sowing. Roots tend to split when heavy water follows a dry spell, and turn pithy when left too long in warm weather, stressed by drought, or held through long hard freezes.
- What vegetables can I still plant in fall?Count back from your first fall frost: radishes and arugula need about 6 weeks, lettuce and spinach 7 to 8, roots and fall cabbage-family crops 10 weeks or more. Garlic goes in around the first frost.