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When to Plant Amaranth in Siskiyou County, CA

Siskiyou County, California Zone 8a May

May in the garden — Siskiyou County, California

A quick May briefing for Siskiyou County, California gardeners — what's urgent, what's next, and what can wait.

Avg. last frost May 15
Avg. first frost October 1
Soil temp (4") 67°F
Watering Critical
Pest pressure Moderate
Daylight 14.3 hrs
  1. Transplant amaranth outside

    Pick a cloudy afternoon or evening to plant. Less transplant shock, and your seedlings will barely blink.

  2. Direct-sow amaranth

    Sow every 2 weeks for a continuous harvest. A single big planting means a single big glut.

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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.

Siskiyou County, California is in USDA Zone 8a. The average last spring frost is May 15 and the first fall frost is October 1, giving you a growing season of approximately 139 days.

At an elevation of 251 feet, Siskiyou County receives approximately 36 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 84°F, so choose short-season varieties of Amaranth to ensure they mature before fall. Sandy soil warms quickly in spring — great for early planting — but Amaranth will need more frequent watering and organic matter to retain nutrients.

Siskiyou County, CA (Zone 8a) Short season
139 days
Last Spring Frost May 15
139 growing days
First Fall Frost October 1

Siskiyou County Soil Profile

Soil Type

Sandy Loam

Soil pH

6-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 18 Transplant: May 20 🍅 Harvest: Aug 19 – Oct 7
Recommended (50%) ✗ May not fit
Start indoors: Mar 27 Transplant: May 29 🍅 Harvest: Aug 28 – Oct 16
Safe Start (90%) ✗ May not fit
Start indoors: Apr 30 Transplant: Jul 2 🍅 Harvest: Oct 1 – Nov 19

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 Siskiyou County

How your county's soil matches Amaranth's growing requirements.

Soil pH

Your soil pH (6.0–6.9) is within Amaranth's preferred range (6.0–7.5).

Soil Texture

Sandy soil in Siskiyou County warms quickly in spring but drains fast. Amaranth will need more frequent watering and regular compost additions to retain nutrients.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Amaranth.

How to Plant Amaranth

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

Monthly Watering Guide for Amaranth

Amaranth needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Amaranth Needs Rainfall You Supplement Action
Jan 7.3" 0" ❄️ Dormant
Feb 7.1" 0" ❄️ Dormant
Mar 5.3" 0" ❄️ Dormant
Apr 3.3" 0" ❄️ Dormant
May 4.3" 1" 3.3" 🚿 Regular watering
Jun 4.3" 0.2" 4.1" 🚿 Regular watering
Jul 4.3" 0" 4.3" 🚿 Regular watering
Aug 4.3" 0" 4.3" 🚿 Regular watering
Sep 4.3" 0.4" 3.9" 🚿 Regular watering
Oct 4.3" 1.6" 2.7" 🚿 Regular watering
Nov 3.1" 0" ❄️ Dormant
Dec 6.7" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Siskiyou County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Amaranth 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.

Amaranth needs ~1,365 GDD — county provides 1,807 GDD Excellent fit

Amaranth Planting Timeline — Siskiyou County, CA

Amaranth Planting Calendar

Activity When Date Range
Start Indoors March 27 Mar 27 – Apr 10
Transplant Outdoors May 29 May 29 – Jun 12
Direct Sow May 22 May 22 – Jun 12
Harvest August 28 Aug 28 – Oct 16

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

90–120 days

🧪 Soil pH

Needs 6–7.5 · Your soil: ideal

🗺️ USDA Zone

Zone 8a

📆 Growing Season

139 days in Siskiyou County

Growing Tips for Amaranth in Siskiyou County

Direct sow Amaranth outdoors after May 15 in Siskiyou County when soil has warmed and frost danger has passed.

Sandy soil in Siskiyou County dries quickly — mulch Amaranth with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.

General growing tips

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

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Amaranth in Siskiyou County, CA?

Siskiyou County is in Zone 8a with an average last frost of May 15. Plan your Amaranth planting based on this frost date — see the calendar above for exact timing.

What planting zone is Siskiyou County, CA?

Siskiyou County, California is in USDA Hardiness Zone 8a. The average last spring frost is May 15 and first fall frost is October 1.

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Your Siskiyou County Garden Planner — Free

A 24-page printable planner built for Siskiyou County (Zone 8a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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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 Siskiyou County, CA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.