When to Plant Amaranth in Honolulu County, HI
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.
Honolulu County, Hawaii is in USDA Zone 11b. The average last spring frost is January 1 and the first fall frost is December 31, giving you a growing season of approximately 364 days.
At an elevation of 235 feet, Honolulu County receives approximately 44.3 inches of rainfall annually with predominantly silty clay soil. Summer highs average 88°F, providing good warmth for Amaranth during the growing season. Clay soil retains moisture well for Amaranth, but amend with compost to improve drainage and prevent root rot.
Honolulu County Soil Profile
Soil Type
Silty Clay
Soil pH
5.7-6.4
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 Honolulu County
How your county's soil matches Amaranth's growing requirements.
Soil pH
Your soil pH (5.7–6.4) overlaps with Amaranth's range (6.0–7.5), though not a perfect match.
Soil Texture
Your silty clay soil in Honolulu County is workable for Amaranth. Add compost annually to improve structure.
Organic Matter
Organic matter is moderate (3.6%). Annual compost additions will help Amaranth.
How to Plant Amaranth
Plant Water Budget
Water stress score is 6/10 — 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 | 4.3" | 6.4" | 0" | ✅ Rainfall sufficient |
| Feb | 4.3" | 4.7" | 0" | ✅ Rainfall sufficient |
| Mar | 4.3" | 6.2" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| May | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Jun | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Jul | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Aug | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Sep | 4.3" | 2.2" | 2.1" | 💧 Light watering |
| Oct | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Nov | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Dec | 4.3" | 6.2" | 0" | ✅ Rainfall sufficient |
Water needs are for active growing months only (Jan–Dec in Honolulu 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 — Honolulu County, HI
Amaranth Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | November 20 | Nov 20 – Dec 4 |
| Transplant Outdoors | January 8 | Jan 8 – Jan 22 |
| Direct Sow | January 1 | Jan 1 – Jan 22 |
| Harvest | April 9 | Apr 9 – May 28 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Transplant Outdoors Direct Sow |
| February | — |
| March | — |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | Start Indoors |
| December | Start Indoors |
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: acceptable
🗺️ USDA Zone
Zone 11b
📆 Growing Season
364 days in Honolulu County
Growing Tips for Amaranth in Honolulu County
With Honolulu County's clay soil (36% clay), work in 3-4 inches of compost before planting Amaranth. Avoid tilling when soil is wet to prevent compaction.
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 Honolulu County, HI?
Honolulu County is in Zone 11b with an average last frost of January 1. Plan your Amaranth planting based on this frost date — see the calendar above for exact timing.
What planting zone is Honolulu County, HI?
Honolulu County, Hawaii is in USDA Hardiness Zone 11b. The average last spring frost is January 1 and first fall frost is December 31.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Honolulu County gardeners in Zone 11b organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.