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When to Plant Amaranth in Grundy County, IL

Grundy County, Illinois Zone 5b May

Top priorities for Grundy County, Illinois gardeners in May

Your Grundy County, Illinois garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost April 20
Avg. first frost October 17
Soil temp (4") 59°F
Watering Moderate
Pest pressure Low
Daylight 14.3 hrs
  1. Plant out amaranth

    Your last frost (April 20) has passed. These warm-season crops can handle outdoor soil now.

Get ahead of June
  • Starting indoors: amaranth

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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.

Grundy County, Illinois is in USDA Zone 5b. The average last spring frost is April 20 and the first fall frost is October 17, giving you a growing season of approximately 180 days.

At an elevation of 629 feet, Grundy County receives approximately 30.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Amaranth during the growing season.

Grundy County, IL (Zone 5b) Moderate season
180 days
Last Spring Frost April 20
180 growing days
First Fall Frost October 17
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Grundy County Soil Profile

Soil Type

Silt Loam

Soil pH

6.1-7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (28 days to spare)
Start indoors: Feb 17 Transplant: Apr 28 🍅 Harvest: Jul 28 – Sep 15
Recommended (50%) ✓ Fits season (26 days to spare)
Start indoors: Feb 23 Transplant: May 4 🍅 Harvest: Aug 3 – Sep 21
Safe Start (90%) ✓ Fits season (21 days to spare)
Start indoors: Mar 14 Transplant: May 23 🍅 Harvest: Aug 22 – Oct 10

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 Grundy County

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

Soil pH

Your soil pH (6.1–7.0) is within Amaranth's preferred range (6.0–7.5).

Soil Texture

The silt loam soil in Grundy County is excellent for Amaranth — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (3.9%). 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
0.7″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 568 gal / 100 sq ft
Drought risk

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 1.3" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2" 0" ❄️ Dormant
Apr 4.3" 3.2" 1.1" 💧 Light watering
May 4.3" 3.6" 0.7" 💧 Light watering
Jun 4.3" 3.3" 1" 💧 Light watering
Jul 4.3" 3.3" 1" 💧 Light watering
Aug 4.3" 3.5" 0.8" 💧 Light watering
Sep 4.3" 2.7" 1.6" 💧 Light watering
Oct 4.3" 2" 2.3" 🚿 Regular watering
Nov 2.2" 0" ❄️ Dormant
Dec 1.8" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Oct in Grundy 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 ~1,444 GDD — county provides 2,475 GDD Excellent fit

Amaranth Planting Timeline — Grundy County, IL

Amaranth Planting Calendar

Activity When Date Range
Start Indoors February 23 Feb 23 – Mar 9
Transplant Outdoors May 4 May 4 – May 18
Direct Sow April 27 Apr 27 – May 18
Harvest August 3 Aug 3 – Sep 21

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

Month-by-Month Timeline

MonthActivities
January
February Start Indoors
March Start Indoors
April Direct Sow
May Transplant Outdoors Direct Sow
June
July
August Harvest
September Harvest
October
November
December
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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 5b

📆 Growing Season

180 days in Grundy County

Growing Tips for Amaranth in Grundy County

Direct sow Amaranth outdoors after April 20 in Grundy County when soil has warmed and frost danger has passed.

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 Grundy County, IL?

Grundy County is in Zone 5b with an average last frost of April 20. Plan your Amaranth planting based on this frost date — see the calendar above for exact timing.

What planting zone is Grundy County, IL?

Grundy County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 20 and first fall frost is October 17.

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Your Grundy County Garden Planner — Free

A 24-page printable planner built for Grundy County (Zone 5b). 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 Grundy County, IL. 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.