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When to Plant Amaranth in Alamosa County, CO

Amaranth is an ancient grain crop with edible leaves and seeds, rich in protein and micronutrients. It thrives in warm conditions and is drought-tolerant once established.

Alamosa County, Colorado is in USDA Zone 4b. The average last spring frost is May 31 and the first fall frost is September 19, giving you a growing season of approximately 111 days.

At an elevation of 8,366 feet, Alamosa County receives approximately 18.3 inches of rainfall annually with predominantly loam soil. Summer highs average 81ยฐF, so choose short-season varieties of Amaranth to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Amaranth successfully. Mulch heavily to conserve soil moisture.

Alamosa County, CO (Zone 4b) Short season
111 days
Last Spring Frost May 31
111 growing days
First Fall Frost September 19

Alamosa County Soil Profile

Soil Type

Loam

Soil pH

6.4-8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 24 Transplant: Jun 16 🍅 Harvest: Sep 15 – Nov 3
Recommended (50%) ✗ May not fit
Start indoors: Mar 29 Transplant: Jun 21 🍅 Harvest: Sep 20 – Nov 8
Safe Start (90%) ✗ May not fit
Start indoors: Apr 12 Transplant: Jul 5 🍅 Harvest: Oct 4 – Nov 22

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
0.7″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 365 gal / 100 sq ft
Drought risk

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

Amaranth needs ~1,129 GDD — county provides 1,193 GDD Good fit

Amaranth Planting Timeline โ€” Alamosa County, CO

Amaranth Planting Calendar

Activity When Date Range
Start Indoors March 29 Mar 29 โ€“ Apr 12
Transplant Outdoors June 21 Jun 21 โ€“ Jul 5
Direct Sow June 14 Jun 14 โ€“ Jul 5
Harvest September 20 Sep 20 โ€“ Nov 8

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

90โ€“120 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 4b

Growing Season

111 days

Growing Tips for Alamosa County

Direct sow after last frost when soil is warm. Thin seedlings to 18 inches apart. Harvest leaves when young and tender; harvest seeds when flower heads begin to dry.

Companion Planting

Good Companions

Avoid Planting Near

  • Fennel

Level Up Your Garden

Frequently Asked Questions

When should I plant Amaranth in Alamosa County, CO?

Alamosa County is in Zone 4b with an average last frost of May 31. Plan your Amaranth planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Alamosa County, CO?

Alamosa County, Colorado is in USDA Hardiness Zone 4b. The average last spring frost is May 31 and first fall frost is September 19.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Alamosa County gardeners in Zone 4b 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 Alamosa County, CO. Local conditions may vary. Last updated: April 2026.