When to Plant Mizuna in St. Croix County, WI
Your April game plan for St. Croix County, Wisconsin
Welcome to April in Zone 4b. These are the moves that will have the biggest impact on your growing season.
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Harden off and plant mizuna
Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.
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Direct-sow mizuna
Succession planting is the secret here. Put in a row now, another in 2 weeks, a third in 4.
Mizuna is a mild-flavored Japanese mustard green with feathery, deeply serrated leaves. It is fast-growing and makes an excellent addition to salads and stir-fries.
St. Croix County, Wisconsin is in USDA Zone 4b. The average last spring frost is April 28 and the first fall frost is October 9, giving you a growing season of approximately 164 days.
At an elevation of 1,245 feet, St. Croix County receives approximately 38.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 81°F, so choose short-season varieties of Mizuna to ensure they mature before fall.
St. Croix County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.7
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 St. Croix County
How your county's soil matches Mizuna's growing requirements.
Soil pH
Your soil pH (6.2–6.7) is within Mizuna's preferred range (6.0–7.5).
Soil Texture
The silt loam soil in St. Croix County is excellent for Mizuna — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.8%) — Mizuna will thrive.
How to Plant Mizuna
Fall planting: Sow 12 weeks before your first frost date for a fall harvest.
Succession Planting Mizuna
Sow every 3.4 weeks. Last sowing by Aug 25 to harvest before frost.
For a dedicated fall crop, sow by Jul 17.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Mizuna
Mizuna needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Mizuna Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.8" | 0" | ❄️ Dormant |
| Apr | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| May | 4.3" | 4.9" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jul | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Aug | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Oct | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in St. Croix County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Mizuna 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.
Mizuna Planting Timeline — St. Croix County, WI
Mizuna Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 17 | Mar 17 – Mar 31 |
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
| Direct Sow | April 21 | Apr 21 – May 12 |
| Harvest | June 2 | Jun 2 – Jun 30 |
| Fall Sowing | July 17 | Jul 17 – Jul 31 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Fall Sowing |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
30–45 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 4b
📆 Growing Season
164 days in St. Croix County
Growing Tips for Mizuna in St. Croix County
Direct sow Mizuna outdoors after April 28 in St. Croix County when soil has warmed and frost danger has passed.
Your generous 164.0-day season in St. Croix County allows multiple plantings of Mizuna. Sow every 15.0 days for continuous harvest.
Common pests for Mizuna 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. Harvest outer leaves as needed for a cut-and-come-again approach. Mizuna is one of the most cold-tolerant Asian greens.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Mizuna in Other Locations
Frequently Asked Questions
When should I plant Mizuna in St. Croix County, WI?
St. Croix County is in Zone 4b with an average last frost of April 28. Plan your Mizuna planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Croix County, WI?
St. Croix County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is April 28 and first fall frost is October 9.
Your St. Croix County Garden Planner — Free
A 24-page printable planner built for St. Croix County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.