When to Plant Microgreens in St. Louis County, MN
Microgreens are young seedlings of vegetables and herbs harvested at the cotyledon or first true leaf stage. They pack concentrated flavors and nutrients in a tiny package.
St. Louis County, Minnesota is in USDA Zone 3a. The average last spring frost is June 2 and the first fall frost is September 10, giving you a growing season of approximately 100 days.
At an elevation of 531 feet, St. Louis County receives approximately 36.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 78°F, so choose short-season varieties of Microgreens to ensure they mature before fall.
St. Louis County Soil Profile
Soil Type
Silt Loam
Soil pH
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. Louis County
How your county's soil matches Microgreens's growing requirements.
Soil pH
Your soil pH (6.0–7.0) is within Microgreens's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in St. Louis County is excellent for Microgreens — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Microgreens.
Organic Matter
Organic matter is excellent (4.0%) — Microgreens will thrive.
How to Plant Microgreens
Fall planting: Sow 12 weeks before your first frost date for a fall harvest.
Succession Planting Microgreens
Sow every 0.7 weeks. Last sowing by Aug 20 to harvest before frost.
For a dedicated fall crop, sow by Jun 18.
Plant Water Budget
Monthly Watering Guide for Microgreens
Microgreens needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Microgreens Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.7" | 0" | ❄️ Dormant |
| Mar | — | 2.7" | 0" | ❄️ Dormant |
| Apr | — | 3.2" | 0" | ❄️ Dormant |
| May | — | 3.9" | 0" | ❄️ Dormant |
| Jun | 4.3" | 5.1" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Sep | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Oct | — | 2.8" | 0" | ❄️ Dormant |
| Nov | — | 2.3" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Jun–Sep in St. Louis County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Microgreens 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.
Microgreens Planting Timeline — St. Louis County, MN
Microgreens Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 21 | Apr 21 – May 5 |
| Transplant Outdoors | June 2 | Jun 2 – Jun 16 |
| Direct Sow | May 26 | May 26 – Jun 16 |
| Harvest | June 9 | Jun 9 – Jul 7 |
| Fall Sowing | June 18 | Jun 18 – Jul 2 |
Plant 0.5" deep · 2" apart · Rows 6" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors Direct Sow |
| June | Transplant Outdoors Direct Sow Fall Sowing Harvest |
| July | Fall Sowing Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
7–21 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 3a
📆 Growing Season
100 days in St. Louis County
Growing Tips for Microgreens in St. Louis County
Direct sow Microgreens outdoors after June 02 in St. Louis County when soil has warmed and frost danger has passed.
Your generous 100.0-day season in St. Louis County allows multiple plantings of Microgreens. Sow every 3.0 days for continuous harvest.
General growing tips
Sow seeds densely on shallow trays of moist growing medium. Cover until germination, then provide light. Harvest with scissors when 1-3 inches tall. Grow year-round indoors.
Microgreens in Other Locations
Frequently Asked Questions
When should I plant Microgreens in St. Louis County, MN?
St. Louis County is in Zone 3a with an average last frost of June 2. Plan your Microgreens planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Louis County, MN?
St. Louis County, Minnesota is in USDA Hardiness Zone 3a. The average last spring frost is June 2 and first fall frost is September 10.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help St. Louis County gardeners in Zone 3a organize planting dates, track what's growing, and never miss a planting window.
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