When to Plant Bok Choy in Mills County, IA
Your May game plan for Mills County, Iowa
A quick May briefing for Mills County, Iowa gardeners — what's urgent, what's next, and what can wait.
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Fire up the seed-starting tray: bok choy
Bottom-water once the first true leaves appear — it keeps stems dry and knocks back damping-off.
Coming up in June — start thinking about
- First harvests: bok choy
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.
Mills County, Iowa is in USDA Zone 5b. The average last spring frost is April 26 and the first fall frost is October 7, giving you a growing season of approximately 164 days.
At an elevation of 1,355 feet, Mills County receives approximately 35.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Bok Choy during the growing season.
Mills County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-6.8
Drainage
Well Drained
Plant Planting Risk Windows
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 Mills County
How your county's soil matches Bok Choy's growing requirements.
Soil pH
Your soil pH (6.3–6.8) is within Bok Choy's preferred range (6.0–7.5).
Soil Texture
The silt loam soil in Mills County is excellent for Bok Choy — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Bok Choy is a heavy drinker but your soil drains very quickly. Mulch heavily and consider drip irrigation.
Organic Matter
Organic matter is excellent (4.1%) — Bok Choy will thrive.
How to Plant Bok Choy
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Bok Choy
Sow every 4.6 weeks. Last sowing by Aug 08 to harvest before frost.
For a dedicated fall crop, sow by Jul 29.
Plant Water Budget
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 | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.5" | 0" | ❄️ Dormant |
| Apr | 3" | 3" | 0" | ✅ Rainfall sufficient |
| May | 3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jun | 3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Jul | 3" | 4.2" | 0" | ✅ Rainfall sufficient |
| Aug | 3" | 3.5" | 0" | ✅ Rainfall sufficient |
| Sep | 3" | 3.3" | 0" | ✅ Rainfall sufficient |
| Oct | 3" | 2.6" | 0.4" | 💧 Light watering |
| Nov | — | 2.3" | 0" | ❄️ Dormant |
| Dec | — | 2.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Mills 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 Planting Timeline — Mills County, IA
Bok Choy Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 22 | Mar 22 – Apr 5 |
| Transplant Outdoors | April 26 | Apr 26 – May 10 |
| Direct Sow | April 12 | Apr 12 – May 3 |
| Harvest | June 7 | Jun 7 – Jul 12 |
| Fall Sowing | July 29 | Jul 29 – Aug 12 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Fall Sowing Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.7"/week · Only during dry spells
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
164 days in Mills County
Growing Tips for Bok Choy in Mills County
Direct sow Bok Choy outdoors after April 26 in Mills County when soil has warmed and frost danger has passed.
Your generous 164.0-day season in Mills County allows multiple plantings of Bok Choy. Sow every 20.0 days for continuous harvest.
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
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Check more plant combinations with our Companion Planting Checker →
Bok Choy in Other Locations
Frequently Asked Questions
When should I plant Bok Choy in Mills County, IA?
Mills County is in Zone 5b with an average last frost of April 26. Plan your Bok Choy planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mills County, IA?
Mills County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 26 and first fall frost is October 7.
Your Mills County Garden Planner — Free
A 24-page printable planner built for Mills County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.