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When to Plant Bok Choy in Big Horn County, WY

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.

Big Horn County, Wyoming is in USDA Zone 4a. The average last spring frost is May 9 and the first fall frost is October 2, giving you a growing season of approximately 146 days.

At an elevation of 7,668 feet, Big Horn County receives approximately 13.7 inches of rainfall annually with predominantly loam soil. Summer highs average 84ยฐF, so choose short-season varieties of Bok Choy to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Bok Choy successfully. Mulch heavily to conserve soil moisture.

Big Horn County, WY (Zone 4a) Short season
146 days
Last Spring Frost May 9
146 growing days
First Fall Frost October 2

Big Horn County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (63 days to spare)
Start indoors: Mar 23 Transplant: May 4 🍅 Harvest: Jun 15 – Jul 20
Recommended (50%) ✓ Fits season (69 days to spare)
Start indoors: Mar 28 Transplant: May 9 🍅 Harvest: Jun 20 – Jul 25
Safe Start (90%) ✓ Fits season (72 days to spare)
Start indoors: Apr 7 Transplant: May 19 🍅 Harvest: Jun 30 – Aug 4

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
0.4″/week
You supply
1.3″/week
Watering frequency 2-3 times/week
Season total 1,724 gal / 100 sq ft
Drought risk

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

Bok Choy needs ~650 GDD — county provides 1,898 GDD Excellent fit

Bok Choy Planting Timeline โ€” Big Horn County, WY

Bok Choy Planting Calendar

Activity When Date Range
Start Indoors March 28 Mar 28 โ€“ Apr 11
Transplant Outdoors May 9 May 9 โ€“ May 23
Direct Sow May 2 May 2 โ€“ May 23
Fall Sowing July 10 Jul 10 โ€“ Jul 24
Harvest June 20 Jun 20 โ€“ Jul 25

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

Month-by-Month Timeline

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

146 days

Growing Tips for Big Horn 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 Big Horn County, WY?

Big Horn County is in Zone 4a with an average last frost of May 9. Plan your Bok Choy planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Big Horn County, WY?

Big Horn County, Wyoming is in USDA Hardiness Zone 4a. The average last spring frost is May 9 and first fall frost is October 2.

๐ŸŒฑ

Plan Your Garden with Confidence

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

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