When to Plant Tomatoes in Cook County, MN
Your May gardening checklist
Welcome to May in Zone 3b. These are the moves that will have the biggest impact on your growing season.
June will be here before you know it — start on
- Transplants going out: tomatoes
- Direct-sowing: tomatoes
Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.
Cook County, Minnesota is in USDA Zone 3b. The average last spring frost is May 20 and the first fall frost is September 29, giving you a growing season of approximately 132 days.
At an elevation of 1,068 feet, Cook County receives approximately 34.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80°F, so choose short-season varieties of Tomatoes to ensure they mature before fall.
Cook County Soil Profile
Soil Type
Silt Loam
Soil pH
6.1-7.1
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 Cook County
How your county's soil matches Tomatoes's growing requirements.
Soil pH
Your soil pH (6.1–7.1) overlaps with Tomatoes's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Cook County is excellent for Tomatoes — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.4%) — Tomatoes will thrive.
How to Plant Tomatoes
Succession Planting Tomatoes
Sow every 6.9 weeks. Last sowing by Jul 06 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Tomatoes
Tomatoes needs approximately 1.2 inches of water per week (5.2" per month). Here's how your county's rainfall compares month by month.
| Month | Tomatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.5" | 0" | ❄️ Dormant |
| Apr | — | 3.5" | 0" | ❄️ Dormant |
| May | 5.2" | 3.4" | 1.8" | 💧 Light watering |
| Jun | 5.2" | 4.7" | 0.5" | 💧 Light watering |
| Jul | 5.2" | 3.9" | 1.3" | 💧 Light watering |
| Aug | 5.2" | 3" | 2.2" | 💧 Light watering |
| Sep | 5.2" | 3.2" | 2" | 💧 Light watering |
| Oct | — | 2.7" | 0" | ❄️ Dormant |
| Nov | — | 2.5" | 0" | ❄️ Dormant |
| Dec | — | 2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Cook County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tomatoes 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.
Tomatoes Planting Timeline — Cook County, MN
Tomatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 18 | Mar 18 – Apr 1 |
| Transplant Outdoors | June 10 | Jun 10 – Jun 24 |
| Direct Sow | June 3 | Jun 3 – Jun 24 |
| Harvest | August 12 | Aug 12 – Oct 14 |
Plant 0.5" deep · 24" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | — |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.2"/week · Only during dry spells
📅 Days to Maturity
60–85 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 3b
📆 Growing Season
132 days in Cook County
Growing Tips for Tomatoes in Cook County
Direct sow Tomatoes outdoors after May 20 in Cook County when soil has warmed and frost danger has passed.
Common pests for Tomatoes in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.
Recommended Tomatoes Varieties for Cook County
Choose determinate, early-maturing varieties for your short season
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.
Tomatoes in Other Locations
Frequently Asked Questions
When should I plant Tomatoes in Cook County, MN?
Cook County is in Zone 3b with an average last frost of May 20. Plan your Tomatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Cook County, MN?
Cook County, Minnesota is in USDA Hardiness Zone 3b. The average last spring frost is May 20 and first fall frost is September 29.
Your Cook County Garden Planner — Free
A 24-page printable planner built for Cook County (Zone 3b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.