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When to Plant Bok Choy in Washburn County, WI

Washburn County, Wisconsin Zone 4a May

Your May game plan for Washburn County, Wisconsin

May is a pivotal month for Washburn County, Wisconsin gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost May 17
Avg. first frost September 25
Soil temp (4") 50°F
Watering Moderate
Pest pressure Low
Daylight 14.7 hrs
  1. Move bok choy from tray to bed

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

  2. Outdoor sowing time: bok choy

    These tolerate cool soil, so you're not gambling by sowing now.

Looking ahead to June
  • Starting indoors: bok choy
  • First harvests: bok choy

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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.

Washburn County, Wisconsin is in USDA Zone 4a. The average last spring frost is May 17 and the first fall frost is September 25, giving you a growing season of approximately 131 days.

At an elevation of 954 feet, Washburn County receives approximately 32.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 79°F, so choose short-season varieties of Bok Choy to ensure they mature before fall.

Washburn County, WI (Zone 4a) Short season
131 days
Last Spring Frost May 17
131 growing days
First Fall Frost September 25
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Washburn County Soil Profile

Soil Type

Silt Loam

Soil pH

6.1-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (46 days to spare)
Start indoors: Apr 2 Transplant: May 14 🍅 Harvest: Jun 25 – Jul 30
Recommended (50%) ✓ Fits season (54 days to spare)
Start indoors: Apr 5 Transplant: May 17 🍅 Harvest: Jun 28 – Aug 2
Safe Start (90%) ✓ Fits season (53 days to spare)
Start indoors: Apr 20 Transplant: Jun 1 🍅 Harvest: Jul 13 – Aug 17

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.

Soil Compatibility in Washburn County

How your county's soil matches Bok Choy's growing requirements.

Soil pH

Your soil pH (6.1–6.9) is within Bok Choy's preferred range (6.0–7.5).

Soil Texture

The silt loam soil in Washburn County is excellent for Bok Choy — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.3%) — Bok Choy will thrive.

How to Plant Bok Choy

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Fall planting: Sow 12 weeks before your first frost date for a fall harvest.

Succession Planting Bok Choy

3
successive plantings in your 131-day season

Sow every 4.6 weeks. Last sowing by Jul 27 to harvest before frost.

For a dedicated fall crop, sow by Jul 03.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Bok Choy

Bok Choy needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.

Month Bok Choy Needs Rainfall You Supplement Action
Jan 1.4" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 2.2" 0" ❄️ Dormant
Apr 3.5" 0" ❄️ Dormant
May 3" 3.7" 0" ✅ Rainfall sufficient
Jun 3" 3.6" 0" ✅ Rainfall sufficient
Jul 3" 4" 0" ✅ Rainfall sufficient
Aug 3" 3.6" 0" ✅ Rainfall sufficient
Sep 3" 3.1" 0" ✅ Rainfall sufficient
Oct 2.7" 0" ❄️ Dormant
Nov 2.1" 0" ❄️ Dormant
Dec 1.6" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Washburn County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Bok Choy Heat Requirements (GDD)

What are Growing Degree Days (GDD)?

Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.

Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.

Bok Choy needs ~462 GDD — county provides 1,211 GDD Excellent fit

Bok Choy Planting Timeline — Washburn County, WI

Bok Choy Planting Calendar

Activity When Date Range
Start Indoors April 5 Apr 5 – Apr 19
Transplant Outdoors May 17 May 17 – May 31
Direct Sow May 10 May 10 – May 31
Harvest June 28 Jun 28 – Aug 2
Fall Sowing July 3 Jul 3 – Jul 17

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

Month-by-Month Timeline

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

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

0.7"/week · Natural rainfall sufficient

📅 Days to Maturity

40–60 days

🧪 Soil pH

Needs 6–7.5 · Your soil: ideal

🗺️ USDA Zone

Zone 4a

📆 Growing Season

131 days in Washburn County

Growing Tips for Bok Choy in Washburn County

Direct sow Bok Choy outdoors after May 17 in Washburn County when soil has warmed and frost danger has passed.

Common pests for Bok Choy in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

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

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Bok Choy in Washburn County, WI?

Washburn County is in Zone 4a with an average last frost of May 17. Plan your Bok Choy planting based on this frost date — see the calendar above for exact timing.

What planting zone is Washburn County, WI?

Washburn County, Wisconsin is in USDA Hardiness Zone 4a. The average last spring frost is May 17 and first fall frost is September 25.

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Your Washburn County Garden Planner — Free

A 24-page printable planner built for Washburn County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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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 Washburn County, WI. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.