When to Plant Green Beans in Boulder County, CO
Green beans are a warm-season staple available as bush or pole types. Bush beans produce a concentrated harvest while pole beans provide a longer picking season.
Boulder County, Colorado is in USDA Zone 5b. 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 Green Beans during the growing season.
Boulder County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
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 Boulder County
How your county's soil matches Green Beans's growing requirements.
Soil pH
Your soil pH (6.7–8.0) is more alkaline than Green Beans prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Boulder County is excellent for Green Beans — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Green Beans.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Green Beans.
How to Plant Green Beans
Succession Planting Green Beans
Sow every 5.7 weeks. Last sowing by Jul 23 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Green Beans
Green Beans needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.
| Month | Green Beans 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 | 3.9" | 3" | 0.9" | 💧 Light watering |
| Jun | 3.9" | 1.6" | 2.3" | 🚿 Regular watering |
| Jul | 3.9" | 2" | 1.9" | 💧 Light watering |
| Aug | 3.9" | 2.1" | 1.8" | 💧 Light watering |
| Sep | 3.9" | 2.1" | 1.8" | 💧 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.
Green Beans 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.
Green Beans Planting Timeline — Boulder County, CO
Green Beans Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | May 21 | May 21 – Jun 11 |
| Harvest | July 16 | Jul 16 – Sep 10 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Direct Sow |
| June | Direct Sow |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.9"/week · 1-2 times/week
📅 Days to Maturity
50–65 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 5b
📆 Growing Season
135 days in Boulder County
Growing Tips for Green Beans in Boulder County
Direct sow Green Beans outdoors after May 14 in Boulder County when soil has warmed and frost danger has passed.
Common pests for Green Beans in this region include bean beetles and aphids. Use row covers early in the season and inspect plants weekly.
Boulder County receives only 22" of rain annually. Green Beans needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow after last frost when soil is warm. Provide sturdy supports for pole varieties. Pick beans regularly when young and tender to encourage continued production.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Avoid harvesting during damp weather. Isolate 25 ft between varieties.
Green Beans in Other Locations
Frequently Asked Questions
When should I plant Green Beans in Boulder County, CO?
Boulder County is in Zone 5b with an average last frost of May 14. Plan your Green Beans 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 5b. The average last spring frost is May 14 and first fall frost is September 26.
Plan Your Garden with Confidence
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