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When to Plant Amaranth in Douglas 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.

Douglas County, Colorado is in USDA Zone 5b. The average last spring frost is May 22 and the first fall frost is September 20, giving you a growing season of approximately 121 days.

At an elevation of 7,421 feet, Douglas County receives approximately 12.9 inches of rainfall annually with predominantly loam soil. Summer highs average 85ยฐF, providing good warmth for Amaranth during the growing season. With low rainfall, drip irrigation is essential for growing Amaranth successfully. Mulch heavily to conserve soil moisture.

Douglas County, CO (Zone 5b) Short season
121 days
Last Spring Frost May 22
121 growing days
First Fall Frost September 20

Douglas County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 17 Transplant: May 26 🍅 Harvest: Aug 25 – Oct 13
Recommended (50%) ✗ May not fit
Start indoors: Mar 27 Transplant: Jun 5 🍅 Harvest: Sep 4 – Oct 23
Safe Start (90%) ✗ May not fit
Start indoors: Apr 24 Transplant: Jul 3 🍅 Harvest: Oct 2 – Nov 20

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
0.5″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 714 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Amaranth needs ~1,444 GDD — county provides 1,663 GDD Good fit

Amaranth Planting Timeline โ€” Douglas County, CO

Amaranth Planting Calendar

Activity When Date Range
Start Indoors March 27 Mar 27 โ€“ Apr 10
Transplant Outdoors June 5 Jun 5 โ€“ Jun 19
Direct Sow May 29 May 29 โ€“ Jun 19
Harvest September 4 Sep 4 โ€“ Oct 23

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 Direct Sow
June Transplant Outdoors Direct Sow
July โ€”
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

90โ€“120 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 5b

Growing Season

121 days

Growing Tips for Douglas 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 Douglas County, CO?

Douglas County is in Zone 5b with an average last frost of May 22. Plan your Amaranth planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Douglas County, CO?

Douglas County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 22 and first fall frost is September 20.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Douglas County gardeners in Zone 5b 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 Douglas County, CO. Local conditions may vary. Last updated: April 2026.