When To Plant Amaranth

Amaranth seeds need warm soil, so plant them two to three weeks after the last frost. Knowing exactly when to plant amaranth can make the difference between a bumper crop and a disappointing patch. This guide walks you through every timing detail, from soil temperature to regional calendars, so you get it right the first time.

Amaranth is a warm-season crop that hates cold feet. If you plant too early, the seeds rot. Too late, and you miss the full growing season. Let’s break down the perfect planting window.

The short answer: wait until soil temperatures reach at least 65°F (18°C). For most gardeners, that falls two to three weeks after the last spring frost. But let’s get more specific.

Understanding Soil Temperature For Amaranth

Amaranth seeds germinate best when the soil is consistently warm. Cold soil slows germination and invites fungal diseases. Here’s what you need to know:

Minimum soil temp: 60°F (15°C) – seeds may sprout but growth will be slow.
Ideal soil temp: 65–75°F (18–24°C) – fast, even germination.
Maximum soil temp: 85°F (29°C) – still fine, but keep soil moist.

Use a soil thermometer to check. Insert it 2 inches deep in the morning. If it reads below 60°F, wait another week.

Last Frost Date As Your Guide

Your local last frost date is the anchor point. Count forward 2–3 weeks from that date. For example:

If your last frost is April 15, plant amaranth around May 1–May 7.
If your last frost is May 10, plant around May 25–June 1.

Check your hardiness zone online. The USDA Plant Hardiness Zone Map is a reliable resource. Zone 5 gardeners typically plant in late May, while Zone 8 gardeners can start in mid-April.

Regional Planting Calendars

Here’s a quick breakdown by region in the United States:

Northeast (Zones 5–6): Late May to early June. Soil warms slowly here.
Midwest (Zones 5–6): Same as Northeast – wait until after Memorial Day.
Southeast (Zones 7–8): Mid-April to early May. Watch for late frosts.
Southwest (Zones 8–9): March to April. Plant early to avoid extreme heat.
Pacific Northwest (Zones 7–8): Late April to mid-May. Soil can stay cool.
Mountain West (Zones 4–5): June. Short growing season – use transplants.

Starting Amaranth Indoors

If your growing season is short, start seeds indoors 4–6 weeks before the last frost. This gives you a head start. Here’s how:

Fill seed trays with a light potting mix.
Sow seeds ¼ inch deep, 2–3 per cell.
Keep soil moist and warm (70–75°F).
Place under grow lights or in a sunny window.
Harden off seedlings for 7–10 days before transplanting.

Transplant outdoors when soil is warm and nights are above 50°F (10°C). Space plants 12–18 inches apart.

Direct Sowing Amaranth Seeds

Direct sowing is simpler and works well in warm climates. Follow these steps:

Prepare the bed – remove weeds and loosen soil.
Sow seeds ¼ inch deep, 2–3 inches apart.
Water gently after planting.
Thin seedlings to 12–18 inches apart when they have 4 leaves.

Direct sowing works best when soil is consistently above 65°F. If a cold snap hits, cover the bed with row cover or plastic.

Planting Amaranth For Grain

If you want amaranth grain, timing is critical. The plants need 90–120 frost-free days to mature. Count backward from your first fall frost date. For example:

First frost: October 15
Count back 120 days: June 17
Plant by mid-June at the latest.

Grain amaranth varieties like ‘Burgundy’ or ‘Golden Giant’ need full sun and consistent moisture. Harvest when the seed heads are dry and brown.

Planting Amaranth For Leaves

For leafy greens, you can plant amaranth in succession. Sow a new batch every 2–3 weeks until 8 weeks before the first frost. This gives you a steady supply of tender leaves.

First planting: 2–3 weeks after last frost.
Second planting: 3 weeks later.
Third planting: 3 weeks after that.

Harvest leaves when they are 4–6 inches long. Pinch off the top to encourage bushier growth.

Planting Amaranth For Ornamental Use

Ornamental amaranths like ‘Love Lies Bleeding’ or ‘Joseph’s Coat’ add drama to gardens. Plant them at the same time as grain varieties. They need warm soil and full sun.

For best color, plant after all frost danger has passed. These varieties are sensitive to cold and may wilt if temperatures drop below 50°F at night.

Common Mistakes With Amaranth Planting

Here are mistakes to avoid:

Planting too early: Seeds rot in cold soil. Wait for warmth.
Planting too deep: Amaranth seeds need light to germinate. Sow shallow.
Overcrowding: Thin seedlings early. Crowded plants produce less.
Ignoring frost: A late frost kills young plants. Use row covers.
Poor soil prep: Amaranth likes well-drained soil with organic matter.

Succession Planting For Continuous Harvest

Succession planting extends your harvest. Here’s a simple schedule:

Early summer: Plant first batch for leaves and grain.
Mid-summer: Plant second batch for fall leaves.
Late summer: Plant third batch for baby greens.

Stop planting 8 weeks before the first fall frost. This ensures the last batch has time to mature.

Growing Amaranth In Containers

Container growing works well for amaranth. Choose a pot at least 12 inches deep and wide. Fill with quality potting soil. Plant 2–3 seeds per pot, then thin to one strong seedling.

Place containers in full sun. Water when the top inch of soil feels dry. Container plants may need more frequent watering than in-ground ones.

Companion Planting With Amaranth

Amaranth pairs well with many vegetables. Good companions include:

Corn – amaranth provides ground cover.
Beans – they fix nitrogen for amaranth.
Squash – amaranth shades the soil.
Tomatoes – amaranth attracts beneficial insects.

Avoid planting amaranth near fennel or potatoes. These plants compete for nutrients.

Pests And Diseases To Watch For

Amaranth is generally hardy, but watch for these issues:

Aphids: Spray with neem oil or insecticidal soap.
Flea beetles: Use row covers early in the season.
Root rot: Avoid overwatering and ensure good drainage.
Powdery mildew: Space plants for air circulation.

Healthy plants resist pests better. Keep soil fertile and water consistently.

Harvesting Amaranth At The Right Time

Harvest timing depends on your goal:

Leaves: Pick when 4–6 inches long, before they get tough.
Grain: Wait until seed heads are dry and rattle when shaken.
Ornamental: Cut stems when flowers are fully developed.

For grain, cut the entire seed head and hang it upside down in a dry, ventilated area. Rub the heads to release seeds.

Storing Amaranth Seeds

Store harvested seeds in a cool, dark place. Use airtight containers. Properly stored seeds last 2–3 years. Label containers with the variety and harvest date.

For next year’s planting, save seeds from your best plants. Let them dry completely before storing.

Adjusting For Climate Change

Weather patterns are shifting. Your last frost date may be earlier or later than historical averages. Keep a garden journal to track your local conditions. Use weather apps for real-time data.

If springs are getting warmer, plant a week earlier. If frosts come later, delay planting. Flexibility is key.

Frequently Asked Questions

Can I Plant Amaranth In The Fall?

Fall planting is possible in warm climates (Zones 9–11). Plant 8–10 weeks before the first frost. In cooler zones, spring planting is more reliable.

How Deep Should I Plant Amaranth Seeds?

Sow seeds ¼ inch deep. They need light to germinate, so don’t bury them too deep. Press them gently into the soil.

What Happens If I Plant Amaranth Too Early?

Seeds may rot in cold, wet soil. Germination is slow and uneven. Young plants may be stunted or killed by a late frost.

Can I Plant Amaranth In Partial Shade?

Amaranth grows best in full sun (6–8 hours daily). Partial shade reduces yield and makes plants leggy. Choose a sunny spot.

How Long Does Amaranth Take To Grow?

Leaves are ready in 30–40 days. Grain takes 90–120 days. Ornamental varieties bloom in 60–90 days. Check seed packets for specific times.

Should I Soak Amaranth Seeds Before Planting?

Soaking is not necessary. Amaranth seeds are small and germinate quickly in warm soil. Direct sow or start indoors without soaking.

Can I Plant Amaranth After Tomatoes?

Yes, amaranth is a good follow-up crop. It uses different nutrients than tomatoes. Rotate crops to prevent soil-borne diseases.

Now you have a complete guide for when to plant amaranth. Check your soil temperature, watch the frost dates, and choose the right method for your garden. With proper timing, you’ll enjoy a bountiful harvest of leaves, grain, or colorful flowers. Happy planting.