When to Plant Amaranth in Marin County, CA
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.
Marin County, California is in USDA Zone 10a. The average last spring frost is February 26 and the first fall frost is November 26, giving you a growing season of approximately 273 days.
At an elevation of 302 feet, Marin County receives approximately 36 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 81°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.
Marin County Soil Profile
Soil Type
Sandy Loam
Soil pH
6-6.9
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 Marin 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 Marin 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 (2.3%). Annual compost additions will help Amaranth.
How to Plant Amaranth
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
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 | — | 7.2" | 0" | ❄️ Dormant |
| Feb | 4.3" | 6.5" | 0" | ✅ Rainfall sufficient |
| Mar | 4.3" | 6.2" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| 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" | 1.4" | 2.9" | 🚿 Regular watering |
| Nov | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Dec | — | 6.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Marin 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 Planting Timeline — Marin County, CA
Amaranth Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 15 | Jan 15 – Jan 29 |
| Transplant Outdoors | March 5 | Mar 5 – Mar 19 |
| Direct Sow | February 26 | Feb 26 – Mar 19 |
| Harvest | June 4 | Jun 4 – Jul 23 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | — |
| May | — |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 10a
📆 Growing Season
273 days in Marin County
Growing Tips for Amaranth in Marin County
Direct sow Amaranth outdoors after February 26 in Marin County when soil has warmed and frost danger has passed.
Sandy soil in Marin 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
Check more plant combinations with our Companion Planting Checker →
Amaranth in Other Locations
Frequently Asked Questions
When should I plant Amaranth in Marin County, CA?
Marin County is in Zone 10a with an average last frost of February 26. Plan your Amaranth planting based on this frost date — see the calendar above for exact timing.
What planting zone is Marin County, CA?
Marin County, California is in USDA Hardiness Zone 10a. The average last spring frost is February 26 and first fall frost is November 26.
Plan Your Garden with Confidence
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