When to Plant Broccoli in Roosevelt County, MT
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.
Roosevelt County, Montana is in USDA Zone 3b. The average last spring frost is May 17 and the first fall frost is September 18, giving you a growing season of approximately 124 days.
At an elevation of 7,123 feet, Roosevelt County receives approximately 19.8 inches of rainfall annually with predominantly loam soil. Summer highs average 78°F, so choose short-season varieties of Broccoli to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Broccoli successfully. Mulch heavily to conserve soil moisture.
Roosevelt County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.7
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.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Broccoli Planting Timeline — Roosevelt County, MT
Broccoli Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 5 | Apr 5 – Apr 19 |
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Direct Sow | May 10 | May 10 – May 31 |
| Fall Sowing | June 26 | Jun 26 – Jul 10 |
| Harvest | July 19 | Jul 19 – Aug 30 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Fall Sowing |
| 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 3b
Growing Season
124 days
Growing Tips for Roosevelt 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 Roosevelt County, MT?
Roosevelt County is in Zone 3b with an average last frost of May 17. Plan your Broccoli planting based on this frost date — see the calendar above for exact timing.
What planting zone is Roosevelt County, MT?
Roosevelt County, Montana is in USDA Hardiness Zone 3b. The average last spring frost is May 17 and first fall frost is September 18.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Roosevelt County gardeners in Zone 3b organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.