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When to Plant Bok Choy in Mercer County, ND

Bok choy is a Chinese cabbage variety with crisp white stalks and dark green leaves. It is a fast-growing cool-season crop ideal for stir-fries and soups.

Mercer County, North Dakota is in USDA Zone 4a. The average last spring frost is May 16 and the first fall frost is September 24, giving you a growing season of approximately 131 days.

At an elevation of 1,118 feet, Mercer County receives approximately 23 inches of rainfall annually with predominantly loam soil. Summer highs average 83ยฐF, so choose short-season varieties of Bok Choy to ensure they mature before fall.

Mercer County, ND (Zone 4a) Short season
131 days
Last Spring Frost May 16
131 growing days
First Fall Frost September 24

Mercer County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.5

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (54 days to spare)
Start indoors: Mar 30 Transplant: May 11 🍅 Harvest: Jun 22 – Jul 27
Recommended (50%) ✓ Fits season (54 days to spare)
Start indoors: Apr 4 Transplant: May 16 🍅 Harvest: Jun 27 – Aug 1
Safe Start (90%) ✓ Fits season (52 days to spare)
Start indoors: Apr 18 Transplant: May 30 🍅 Harvest: Jul 11 – Aug 15

Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.

Plant Water Budget

Plant needs
1.5″/week
Rainfall provides
0.7″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 1,067 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Bok Choy needs ~612 GDD — county provides 1,604 GDD Excellent fit

Bok Choy Planting Timeline โ€” Mercer County, ND

Bok Choy Planting Calendar

Activity When Date Range
Start Indoors April 4 Apr 4 โ€“ Apr 18
Transplant Outdoors May 16 May 16 โ€“ May 30
Direct Sow May 9 May 9 โ€“ May 30
Fall Sowing July 2 Jul 2 โ€“ Jul 16
Harvest June 27 Jun 27 โ€“ Aug 1

Plant 1" deep ยท 15" apart ยท Rows 24" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April Start Indoors
May Transplant Outdoors Direct Sow
June Harvest
July Fall Sowing Harvest
August Harvest
September โ€”
October โ€”
November โ€”
December โ€”

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

High โ€” keep soil consistently moist

Days to Maturity

40โ€“60 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 4a

Growing Season

131 days

Growing Tips for Mercer County

Direct sow in spring or fall for best results. Keep soil consistently moist. Harvest whole heads or cut outer leaves for a cut-and-come-again approach.

Companion Planting

Good Companions

Avoid Planting Near

  • Strawberries

Level Up Your Garden

Frequently Asked Questions

When should I plant Bok Choy in Mercer County, ND?

Mercer County is in Zone 4a with an average last frost of May 16. Plan your Bok Choy planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Mercer County, ND?

Mercer County, North Dakota is in USDA Hardiness Zone 4a. The average last spring frost is May 16 and first fall frost is September 24.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Mercer County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.

Get Your Free Garden Planner →

Free download. Plan your entire garden season in minutes.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Mercer County, ND. Local conditions may vary. Last updated: April 2026.