Minnesota gardeners have a narrow window, planting bok choy in May and again in August for a fall harvest. Knowing the best time to plant bok choy in minnesota is key to getting a good crop before the heat or frost hits. This guide walks you through the exact timing, soil prep, and care needed for success in the North Star State.
Bok choy is a cool-season crop that bolts quickly in hot weather. In Minnesota, spring and fall are your only reliable seasons. The trick is to plant early enough to beat the summer heat, and late enough to avoid a hard freeze in autumn.
Best Time To Plant Bok Choy In Minnesota
The absolute best time to plant bok choy in minnesota is two weeks before the last expected frost in spring. For most of the state, that means late April to early May. For a fall crop, plant about 8 to 10 weeks before the first fall frost, which is usually mid-August.
Bok choy seeds germinate best when soil temperatures are between 40°F and 75°F. If you plant too early in cold, wet soil, seeds may rot. Wait until the ground is workable and not waterlogged.
Spring Planting Window
In southern Minnesota (Zones 4b-5a), aim for late April to early May. In northern Minnesota (Zones 3a-4a), wait until mid-May. Use a soil thermometer to check—soil should be at least 40°F.
- Southern MN: April 25 to May 10
- Central MN: May 1 to May 15
- Northern MN: May 10 to May 25
If you start seeds indoors, sow them 4 to 6 weeks before your last frost date. Harden off seedlings for a week before transplanting. This gives you a head start on the short season.
Fall Planting Window
For a fall harvest, plant bok choy in mid-August. This timing lets the plants mature during cooler September weather. Bok choy actually tastes sweeter after a light frost.
- Count back 8-10 weeks from your average first fall frost date.
- For southern MN, that’s around August 10-20.
- For northern MN, aim for August 1-10.
Fall planting avoids the bolting problem that plagues spring crops. The shorter days and cooler nights keep bok choy tender and mild.
Why Timing Matters So Much In Minnesota
Bok choy is a biennial that thinks it’s an annual in Minnesota. It wants to flower and set seed when days get long and hot. If you plant too late in spring, the plant will bolt—send up a flower stalk—and turn bitter.
Minnesota’s summers are short but intense. Temperatures above 80°F stress bok choy. The plant responds by going to seed quickly. That’s why the spring window is so narrow.
Bolting Triggers
- Daytime temps above 75°F for several days
- Soil temperatures above 80°F
- Long daylight hours (14+ hours)
Fall planting avoids all these triggers. Days are getting shorter, and temperatures are dropping. Your bok choy will stay in the leafy growth stage longer.
Preparing Your Garden For Bok Choy
Bok choy grows best in rich, well-draining soil with a pH between 6.0 and 7.5. Minnesota’s clay soil can be heavy, so amend it with compost or aged manure. Work the soil to a depth of 8-10 inches.
Choose a spot that gets full sun to partial shade. In spring, full sun is fine. For fall planting, a spot with afternoon shade can help keep soil cooler.
Soil Preparation Steps
- Test your soil pH. Add lime if below 6.0, sulfur if above 7.5.
- Mix in 2-3 inches of compost.
- Add a balanced fertilizer (10-10-10) at planting time.
- Rake the bed smooth and water it well a day before planting.
Bok choy is a heavy feeder. It needs plenty of nitrogen for leaf growth. Side-dress with compost or a nitrogen-rich fertilizer halfway through the growing season.
How To Plant Bok Choy Seeds
Sow seeds ¼ to ½ inch deep. Space seeds 6 inches apart in rows 18-24 inches apart. If you’re planting in a raised bed, you can space them 8-10 inches apart in all directions.
Water the seeds gently after planting. Keep the soil moist but not soggy until seedlings emerge, which takes 4-8 days. Thin seedlings to 6-8 inches apart once they have two true leaves.
Transplanting Seedlings
If you started seeds indoors, harden them off over a week. Set them outside for a few hours each day, gradually increasing time. Transplant on a cloudy day or in the evening to reduce transplant shock.
- Space transplants 8-10 inches apart.
- Water deeply after planting.
- Use row covers if a late frost threatens.
Bok choy roots are shallow, so handle seedlings carefully. Don’t let them get root-bound in pots.
Caring For Your Bok Choy
Consistent moisture is critical. Bok choy needs about 1 inch of water per week. Mulch with straw or grass clippings to retain moisture and keep roots cool.
Watch for pests like flea beetles and cabbage worms. Use floating row covers to protect young plants. If you see aphids, spray them off with a strong stream of water.
Fertilizing Schedule
Feed bok choy every two weeks with a liquid fertilizer. Use a balanced formula like 10-10-10 or a fish emulsion. Stop fertilizing once the heads start to form.
- Apply fertilizer at planting time.
- Side-dress with compost after 3 weeks.
- Use liquid feed every 2 weeks until harvest.
Over-fertilizing can cause lush growth that attracts pests. Stick to the schedule and watch your plants.
Harvesting Bok Choy At The Right Time
Bok choy is ready to harvest in 45-60 days from seeding. For baby bok choy, harvest when plants are 4-6 inches tall. For full-size heads, wait until they are 10-12 inches tall and the stems are thick.
Cut the whole plant at the base, just above the soil line. You can also harvest outer leaves as needed, leaving the inner rosette to keep growing.
Signs Your Bok Choy Is Ready
- Stems are firm and crisp
- Leaves are dark green and glossy
- Plant has a compact, upright shape
- No flower stalk has started to form
If you see a flower stalk starting, harvest immediately. The plant will get bitter quickly. Don’t wait.
Common Problems And Solutions
Bok choy is generally easy to grow, but Minnesota gardeners face a few challenges. Here’s how to handle them.
Bolting
If your bok choy bolts, it’s usually because of heat or stress. Plant earlier in spring or later in fall. Use shade cloth if a heat wave hits.
Pests
Flea beetles leave small holes in leaves. Use row covers or diatomaceous earth. Cabbage worms are green caterpillars that eat leaves. Hand-pick them or use BT (Bacillus thuringiensis).
Diseases
Downy mildew shows as yellow spots on leaves. Avoid overhead watering and space plants for good air circulation. Clubroot causes swollen roots and stunted growth. Rotate crops and avoid planting in infected soil.
Extending The Harvest Season
You can plant successions every 2 weeks in spring and fall. This gives you a continuous supply. In spring, stop planting once temperatures consistently hit 75°F.
For fall, you can plant until 6 weeks before the first frost. Use cold frames or row covers to protect plants from early frosts. Bok choy can survive light frosts, but hard freezes will kill it.
Using Cold Frames
A cold frame can extend your fall harvest by 4-6 weeks. Build a simple frame with old windows or buy a kit. Place it over your bok choy bed in late September.
- Vent the cold frame on warm days to prevent overheating.
- Water plants less frequently in cooler weather.
- Harvest before the frame gets too cold (below 20°F).
With a cold frame, you can harvest bok choy into November in southern Minnesota.
Best Varieties For Minnesota
Choose varieties that mature quickly and resist bolting. Here are top picks for Minnesota gardens.
- ‘Joi Choi’: Slow to bolt, good for spring and fall.
- ‘Win-Win’: Compact, cold-tolerant, great for fall.
- ‘Shanghai Green’: Fast-growing, tender leaves.
- ‘Toy Choi’: Baby bok choy, ready in 30 days.
All these varieties do well in Minnesota’s climate. Look for seeds at local garden centers or online.
Frequently Asked Questions
Can I plant bok choy in July in Minnesota?
July is too hot for bok choy in Minnesota. The heat will cause bolting. Wait until mid-August for a fall crop.
How late can I plant bok choy in Minnesota for fall?
You can plant bok choy up to 6 weeks before the first expected frost. In southern MN, that’s early September. In northern MN, aim for late August.
Do I need to start bok choy seeds indoors?
No, direct sowing works well. But starting indoors gives you a 2-3 week head start in spring. It’s optional.
What is the best soil temperature for bok choy germination?
Bok choy seeds germinate best between 40°F and 75°F. Soil temps around 60°F are ideal.
Can I grow bok choy in containers in Minnesota?
Yes, use a pot at least 8 inches deep. Place it in a spot with morning sun and afternoon shade. Water frequently, as containers dry out fast.
Final Tips For Success
Keep a garden journal to track your planting dates and results. Minnesota’s weather varies year to year, so adjust your schedule based on actual conditions.
Mulch heavily in fall to protect plants from early frosts. Use row covers for extra protection. And don’t forget to water consistently—bok choy is 95% water and needs steady moisture.
With the right timing, you can enjoy fresh bok choy from your Minnesota garden in spring and fall. The key is to plant early in spring and again in late summer. Follow these guidelines, and you’ll have a bountiful harvest.
Remember, the best time to plant bok choy in minnesota is two weeks before the last frost in spring and eight weeks before the first frost in fall. Stick to these windows, and your bok choy will thrive.