When to Plant Broccoli in Adams County, CO
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.
Adams County, Colorado is in USDA Zone 5b. The average last spring frost is May 4 and the first fall frost is October 5, giving you a growing season of approximately 154 days.
At an elevation of 5,827 feet, Adams County receives approximately 23.9 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Broccoli during the growing season.
Adams County Soil Profile
Soil Type
Loam
Soil pH
6.6-7.7
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 — Adams County, CO
Broccoli Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 30 | Mar 30 – Apr 13 |
| Transplant Outdoors | May 4 | May 4 – May 18 |
| Direct Sow | April 20 | Apr 20 – May 11 |
| Fall Sowing | July 27 | Jul 27 – Aug 10 |
| Harvest | July 6 | Jul 6 – Aug 17 |
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 | Fall Sowing 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 5b
Growing Season
154 days
Growing Tips for Adams 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 Adams County, CO?
Adams County is in Zone 5b with an average last frost of May 4. Plan your Broccoli planting based on this frost date — see the calendar above for exact timing.
What planting zone is Adams County, CO?
Adams County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 4 and first fall frost is October 5.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Adams County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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