When to Plant Broccoli in Rock County, MN
Broccoli is a nutrient-dense cool-season crop that produces large central heads followed by smaller side shoots. It is one of the most popular garden vegetables.
Rock County, Minnesota is in USDA Zone 4b. The average last spring frost is May 2 and the first fall frost is October 2, giving you a growing season of approximately 153 days.
At an elevation of 916 feet, Rock County receives approximately 32.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 82°F, so choose short-season varieties of Broccoli to ensure they mature before fall.
Rock County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.9
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.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Broccoli Planting Timeline — Rock County, MN
Broccoli Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 21 | Mar 21 – Apr 4 |
| Transplant Outdoors | May 2 | May 2 – May 16 |
| Direct Sow | April 25 | Apr 25 – May 16 |
| Fall Sowing | July 10 | Jul 10 – Jul 24 |
| Harvest | July 4 | Jul 4 – Aug 15 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
60–90 days
Soil pH
6 – 7
USDA Zone
Zone 4b
Growing Season
153 days
Growing Tips for Rock County
Start seeds indoors 6-8 weeks before last frost. Provide consistent moisture to prevent hollow stems. Harvest heads before yellow flowers appear.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Isolate 1/2 mile from other brassicas. Biennial — must overwinter roots.
Broccoli in Other Locations
Frequently Asked Questions
When should I plant Broccoli in Rock County, MN?
Rock County is in Zone 4b with an average last frost of May 2. Plan your Broccoli planting based on this frost date — see the calendar above for exact timing.
What planting zone is Rock County, MN?
Rock County, Minnesota is in USDA Hardiness Zone 4b. The average last spring frost is May 2 and first fall frost is October 2.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Rock County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.
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