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When to Plant Fava Beans in San Juan County, CO

Fava beans are a cool-season legume with large, meaty beans inside thick pods. They fix nitrogen in the soil and are one of the oldest cultivated crops.

San Juan County, Colorado is in USDA Zone 4a. The average last spring frost is June 18 and the first fall frost is September 8, giving you a growing season of approximately 82 days.

At an elevation of 7,539 feet, San Juan County receives approximately 20.1 inches of rainfall annually with predominantly loam soil. Summer highs average 82ยฐF, so choose short-season varieties of Fava Beans to ensure they mature before fall.

San Juan County, CO (Zone 4a) Very short season
82 days
Last Spring Frost June 18
82 growing days
First Fall Frost September 8

San Juan County Soil Profile

Soil Type

Loam

Soil pH

6.3-8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 26 Transplant: Jun 7 🍅 Harvest: Aug 23 – Oct 4
Recommended (50%) ✗ May not fit
Start indoors: May 7 Transplant: Jun 18 🍅 Harvest: Sep 3 – Oct 15
Safe Start (90%) ✗ May not fit
Start indoors: May 18 Transplant: Jun 29 🍅 Harvest: Sep 14 – Oct 26

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

Plant needs
1.0″/week
Rainfall provides
1.0″/week
You supply
0.3″/week
Watering frequency 1-2 times/week
Season total 237 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Fava Beans needs ~1,006 GDD — county provides 943 GDD Tight fit

Fava Beans Planting Timeline โ€” San Juan County, CO

Fava Beans Planting Calendar

Activity When Date Range
Start Indoors May 7 May 7 โ€“ May 21
Transplant Outdoors June 18 Jun 18 โ€“ Jul 2
Direct Sow June 11 Jun 11 โ€“ Jul 2
Fall Sowing June 16 Jun 16 โ€“ Jun 30
Harvest September 3 Sep 3 โ€“ Oct 15

Plant 1" deep ยท 15" apart ยท Rows 24" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May Start Indoors
June Transplant Outdoors Direct Sow Fall Sowing
July Transplant Outdoors Direct Sow
August โ€”
September Harvest
October Harvest
November โ€”
December โ€”

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

75โ€“100 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 4a

Growing Season

82 days

Growing Tips for San Juan County

Direct sow as early as soil can be worked in spring. Pinch growing tips when pods begin to form to redirect energy and reduce aphid problems. Stake tall varieties.

Companion Planting

Good Companions

Avoid Planting Near

  • Onion
  • Garlic

Level Up Your Garden

Frequently Asked Questions

When should I plant Fava Beans in San Juan County, CO?

San Juan County is in Zone 4a with an average last frost of June 18. Plan your Fava Beans planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is San Juan County, CO?

San Juan County, Colorado is in USDA Hardiness Zone 4a. The average last spring frost is June 18 and first fall frost is September 8.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help San Juan County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for San Juan County, CO. Local conditions may vary. Last updated: April 2026.