When to plant Broccoli Rabe in Boulder County, CO
In Zone 6a (Boulder County), direct-sow Broccoli Rabe between April 30 and May 21 for spring, after the May 14 last-frost mark. A second sowing from July 18 to August 1 extends the harvest into fall.
When to Plant Broccoli Rabe in Boulder County, CO
Boulder County, Colorado gardeners: here's your June plan
June is a pivotal month for Boulder County, Colorado gardens. Focus on these tasks first and you'll set up the rest of the season for success.
Broccoli rabe (rapini) is a brassica grown for its slightly bitter, nutty-flavored florets, leaves, and stems. It is a staple in Italian cooking.
Boulder County, Colorado is in USDA Zone 6a. The average last spring frost is May 14 and the first fall frost is September 26, giving you a growing season of approximately 135 days.
At an elevation of 7,657 feet, Boulder County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Broccoli Rabe during the growing season.
Boulder County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
Drainage
Well Drained
Broccoli Rabe 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 Boulder County
How your county's soil matches Broccoli Rabe's growing requirements.
Soil pH
Your soil pH (6.7–8.0) overlaps with Broccoli Rabe's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Boulder County is excellent for Broccoli Rabe — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Broccoli Rabe.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Broccoli Rabe.
How to Plant Broccoli Rabe
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Broccoli Rabe
Sow every 4.6 weeks. Last sowing by Jul 28 to harvest before frost.
For a dedicated fall crop, sow by Jul 18.
Broccoli Rabe Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Broccoli Rabe
Broccoli Rabe needs approximately 0.8 inches of water per week (3.5" per month). Here's how your county's rainfall compares month by month.
| Month | Broccoli Rabe Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 3.5" | 3" | 0.5" | 💧 Light watering |
| Jun | 3.5" | 1.6" | 1.9" | 🚿 Regular watering |
| Jul | 3.5" | 2" | 1.5" | 💧 Light watering |
| Aug | 3.5" | 2.1" | 1.4" | 💧 Light watering |
| Sep | 3.5" | 2.1" | 1.4" | 💧 Light watering |
| Oct | — | 1.9" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Boulder County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Broccoli Rabe 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.
Broccoli Rabe Planting Timeline — Boulder County, CO
Broccoli Rabe Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 9 | Apr 9 – Apr 23 |
| Transplant Outdoors | May 14 | May 14 – May 28 |
| Direct Sow | April 30 | Apr 30 – May 21 |
| Harvest | June 25 | Jun 25 – Jul 30 |
| Fall Sowing | July 18 | Jul 18 – Aug 1 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Fall Sowing Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.8"/week · 1-2 times/week
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 6a
📆 Growing Season
135 days in Boulder County
Growing Tips for Broccoli Rabe in Boulder County
Direct sow Broccoli Rabe outdoors after May 14 in Boulder County when soil has warmed and frost danger has passed.
Common pests for Broccoli Rabe in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow in spring or fall. Harvest when small yellow flower buds first appear but before they open. Cut the main shoot first to encourage side shoots.
Companion Planting
Good Companions
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Broccoli Rabe in Other Locations
Frequently Asked Questions
When should I plant Broccoli Rabe in Boulder County, CO?
Boulder County is in Zone 6a with an average last frost of May 14. Plan your Broccoli Rabe planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boulder County, CO?
Boulder County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 14 and first fall frost is September 26.
When should I plant Broccoli Rabe in Boulder County, CO?
In Boulder County, CO, plant Broccoli Rabe after the last frost (around May 14) and before the first frost (around September 26). Best results when soil holds above 50°F.
What growing zone is Boulder County, CO for Broccoli Rabe?
Boulder County sits in USDA Zone 6a. Broccoli Rabe grows reliably in zones 2a through 10b, so it's a good fit here.
Can Broccoli Rabe grow in Boulder County's climate?
Yes — Broccoli Rabe grows well in Boulder County's temperate climate. Boulder County averages a 135-day frost-free season, with last frost around May 14 and first frost around September 26.
Your Boulder County Garden Planner — Free
A 22-page printable planner built for Boulder County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.