How to Grow Amaranth: Sow in 65°F Soil, Pick Leaves From Day 30, Thresh Seed in Fall, and Spot the Pigweed Look-Alike

Amaranth is a warm-season annual that pays you three ways: the tassels and colored foliage fill a border, the young leaves cook like spinach, and the seed heads give a gluten-free grain. The catch is that it shares a genus with pigweed, so the plant you sowed and the weed you pull are close cousins that look alike as seedlings.

This guide covers the soil temperature to wait for, a calendar for each of the three uses, how to harvest and thresh the seed, why the leaves need cooking, and the traits that separate garden amaranth from redroot pigweed. If you have grown celosia from seed, the sowing routine will feel familiar: NC State places plumed cockscomb in the same plant family, Amaranthaceae.

Four Kinds of Amaranth at a Glance

Amaranth is one genus, Amaranthus, grown as a grain, an ornamental, a leafy vegetable or a forage crop, according to the University of Kentucky. The types overlap, so choose by what you want to harvest first. Height and season length differ far more than leaf shape does.

Three pre-planned garden beds, free

Stop staring at empty beds: printable plans with exact layouts, plant lists and planting calendars — yours free from the Garden Library.

Send me the plans

I agree to receive emails from Blooming Expert and accept the Privacy Policy. Unsubscribe anytime.

The takeaway: for the cultivars these sources list, leaves come in about a month, flowers in two to three months and seed in roughly 100 to 110 days, so one dual-purpose plant can be picked for leaves early and left to make seed. Adaptive Seeds, a seed grower, lists ‘Rio San Lorenzo’ at 45 days for leaf and 100 for grain.

When to Sow: Soil Temperature Beats the Calendar

Sow amaranth outdoors when the soil is at least 65°F. The Alternative Field Crops Manual (University of Minnesota and University of Wisconsin) gives 65°F as the floor for late-May sowing, while UF/IFAS recommends waiting for 70°F after the last frost. Prairie View A&M puts the germination range at 64–75°F.

The mechanism is a threshold, not a slope. UF/IFAS reports rapid germination above 68°F, an optimum of 70–75°F (seed up in about a week), and slow or failed germination below 50°F. Cold is also a kill switch: it says plants cannot survive below 40°F because of chilling injury, and the Minnesota and Wisconsin manual calls seedlings very frost-sensitive. Our celosia guide takes the same wait-for-warm-soil approach, with its own 75°F target.

Depth, spacing and the emergence problem

Sow shallow and sow thick. The seed is tiny, about 1 millimeter in grain types and 0.04 inch in leaf types. The Minnesota and Wisconsin manual says no deeper than ½ inch, UF/IFAS gives ⅛ to ¼ inch, and a fine, firm seedbed helps. Kentucky says a 40 to 60 percent emergence rate is not uncommon, and crusting soil lowers it further, so plan on thinning rather than hoping for a perfect stand.

• Leaf crop: UF/IFAS suggests seeds about 1 inch apart in a garden row, thinned to 6 inches.
• Border or grain plants: Adaptive Seeds gives 12–18 inch spacing.
• Transplants: set them out early after the last frost; UF/IFAS warns later transplanting can cause premature flowering.

The slow start

Amaranth grows slowly for its first weeks. Kentucky calls it a poor weed competitor at first; once plants reach 10 to 12 inches they outcompete later weeds, and the Minnesota and Wisconsin manual says growth turns rapid at about a foot. Keep the bed clean until then. A mulch helps, but because the seed is tiny and the seedlings fragile, I would spread it only after seedlings are well up (my rule of thumb; the sources give no date). The mulching guide covers depth and materials.

One Plant, Three Uses: What to Do When

As a border plant

Love-lies-bleeding is the classic border amaranth: NC State describes long, drooping red or gold tassels, around 12 inches, that bloom from summer until frost on plants 3–5 feet tall and 1–2 feet wide. Expect to wait: it does not bloom until about three months after sowing, though a seed seller lists 65 days. NC State says to keep the soil moist and accepts full sun to part shade.

Foliage types such as Joseph’s coat (A. tricolor) behave differently. NC State says they tolerate full sun but need late-afternoon shade, rot if kept too wet, and lose color if over-fertilized. Easy on the fertilizer is a theme: the Minnesota and Wisconsin manual says amaranth can lodge severely under high nitrogen, and UF/IFAS notes plants near 5 feet may need staking.

If it is the petals you want to eat rather than the tassels, see our guide to edible flowers.

For leaves: the harvest window

Pick leaves from about 30 days after sowing. UF/IFAS puts the first harvest at roughly 30 days; Prairie View A&M says 30–55 days, when plants reach about 2 feet. Pick palm-sized leaves or break off leaves around the growing tips, and take only part of the foliage so the plant regrows; UF/IFAS expects another harvest within two weeks.

The window closes when the plant flowers. UF/IFAS says leaves become fewer and unsuitable after flowering starts, and that severe drought triggers early flowering, as does Prairie View A&M’s fact sheet. A second sowing a few weeks later is the logical way to extend the supply (my suggestion; none of the sources give a schedule).

The sources disagree on feeding. Prairie View A&M says leaves need high nitrogen to regrow after cutting; UF/IFAS says excess inorganic nitrogen pales the leaves and builds toxic nitrate, and that fertilizer has not been shown to raise yield dramatically. The Minnesota and Wisconsin manual adds that pigweeds are known nitrate accumulators and amaranth responds similarly. Feed lightly.

Which leaves need cooking?

Cook the leaves of any amaranth you plan to eat in quantity. UF/IFAS says the leaves may contain nitrates and oxalates, which can bind calcium and cause kidney stones in people prone to them; adequate cooking removes them, but eating the plant uncooked in excess (more than 7 ounces a day) may still be a health threat. It also says young, tender leaves are eaten raw in salad mixes. The sources I read do not rank the types by oxalate, so treat all of them alike: raw in small amounts when young, cooked otherwise.

Boiling works because oxalate comes in two forms. A 1978 study in British Journal of Nutrition analyzed Amaranthus leaves raw and after 15 minutes of cooking in 15 times their weight of water, drained. Water-soluble oxalic acid fell from an average of 446 to 30 milligrams per 100 grams, while the water-insoluble fraction (956 raw, 1,009 cooked) did not drop at all. In its feeding tests, six men absorbed less milk calcium when the leaves were cooked without draining the water; when the water was thrown away, absorption was unaffected. The study was small and old, so read it as a mechanism, not a dose. Cooked amaranth is lower in soluble oxalate, not oxalate-free, and boiling also stripped 86–94 percent of the riboflavin, folic acid and vitamin C.

For grain: season length and the harvest test

Grain amaranth needs the longest season of the three uses. The Minnesota and Wisconsin manual says the crop does not mature completely in the upper Midwest’s short season and that a frost is usually needed to kill the plants so they dry enough to harvest. Count back from your first expected frost: Adaptive Seeds lists ‘Rio San Lorenzo’ at about 100 days to grain, so a late-May sowing would reach that stage around early September (my arithmetic, not a sourced date).

Kentucky’s field-scale guidance is to harvest a week to 10 days after a killing frost. Stems and leaves hold moisture, so seeds stick to wet plant material, and waiting too long causes shattering and lodging. At garden scale, Adaptive Seeds says harvest when seeds rub off easily in your hand but before the head is crispy dry; for ‘Rio San Lorenzo’ it adds that the seed should feel hard when bitten, and to get to it before the birds.

1. Dry the heads: Adaptive Seeds says to windrow the plants or hang them over a tarp for several days.
2. Thresh by rubbing or shaking the dry heads, or shaking them in a bag (a seed-saving chart titled Practical Guide for Saving Seeds from Small Gardens suggests the bag).
3. Winnow: Adaptive Seeds stirs the seed in a bowl so the chaff rises to the top.
4. Dry and store: Kentucky says to dry the grain to 10–12 percent moisture; the Minnesota and Wisconsin manual stores it in heavy paper bags or wooden bins.

I found no extension page on hand-threshing at garden scale, so the method above comes from a seed grower and a seed-saving chart, while the frost and moisture numbers come from field-scale extension sheets.

Amaranth or Pigweed? What Separates Them

Do not trust a seedling to tell you which amaranth it is. Kansas State says pigweed identification is difficult in the early seedling stage because many species look the same, and UC IPM says seedlings of all common pigweeds are similar. Neither compares them with garden amaranth, which belongs to the same genus. My working rule, which is an inference rather than a sourced test: treat any amaranth-looking seedling you did not sow, or that sits outside your sown row, as pigweed.

Differences show as plants mature. The table sets garden amaranth against redroot pigweed, the most common one in the sources.

One trap sits in that seed row: seed color alone is not a test. Grain amaranth seed is pale and pigweed seed is dark, but leaf amaranth seed is also brown-black, so a dark seed does not make a plant a weed.

Two harder look-alikes deserve a call to your county extension office. Ohio State says Palmer amaranth and waterhemp are competitive and many populations have developed resistance to several of the most effective herbicide options, and Cornell describes Palmer amaranth as hairless, with white-veined leaf undersides, long leaf stalks and a soft head 1–1.5 feet long. A tall, hairless amaranth you never planted is worth a photo before you compost it.

Reseeding and Weediness: How Much Risk

Garden amaranth may self-seed, but the evidence is mixed and mostly grower experience. UF/IFAS found no evidence that vegetable amaranth is invasive. The Minnesota and Wisconsin manual says grain amaranth seed does not go dormant and the crop has not become a weed where grown. Adaptive Seeds says love-lies-bleeding occasionally self-seeds and can return through volunteers, but is not weedy like pigweed. I found no extension data on how freely it reseeds in home gardens.

Pigweed is the real risk, and its biology explains why. Cornell reports 25,000–120,000 seeds per plant in good conditions, seed that is only moderately persistent but can survive decades in a few cases, and germination stimulated by light, warm soil and nitrate. That is why a freshly dug bed erupts: disturbance brings buried seed to the light. Redroot pigweed emerging in early summer flowered in about 6.5 weeks in one study Cornell cites, with seed maturing 7–8 weeks later, and late-summer plants flowered in as few as 3 weeks, so a weed you ignore in August can still seed.

• Mulch: Cornell says straw and other mulches suppress pigweed because its small seeds carry little energy to push through, though some seedlings penetrate loose straw; use a heavier layer or compact it.
• Manure: Cornell notes cow manure is commonly contaminated with pigweed seed.
• Clean up: UF/IFAS recommends removing all plant material after harvest.
• Heads you do not want seeded: cut them before they dry and shatter (a logical step from the shattering Kentucky describes, not a sourced rule).

Saving seed has its own catch. The seed-saving chart says amaranth is wind-pollinated, will cross with wild amaranth, and needs 800–1,600 feet of isolation or bagged heads; Adaptive Seeds says a quarter mile. Kansas State adds that pigweed species can hybridize. Seed saved from a plot beside weedy amaranth may not come true.

Common Problems, Diagnosed

Frequently Asked Questions

How do you grow amaranth from seed?

Sow outdoors when the soil is at least 65°F, no deeper than ½ inch, in a fine, firm bed. Kentucky says 40–60 percent emergence is not uncommon, so sow a little extra seed, then thin to 6 inches for leaves or 12–18 inches for border and grain plants.

When do you harvest amaranth?

Leaves are ready about 30 days after sowing, and the window ends when the plant flowers. Grain is harvested when seeds rub off easily in your hand but before the head is crispy dry; Kentucky’s field guidance is a week to 10 days after a killing frost.

Is amaranth the same as pigweed?

Both are in the genus Amaranthus. The Minnesota and Wisconsin manual says grain amaranths are different species from redroot pigweed, though a seed-saving chart says amaranth crosses with wild amaranth. Seedlings look alike; mature flower heads differ, and seed color alone is not a test.

Can you eat amaranth leaves raw?

Young, tender leaves can go into salad mixes in small amounts, according to UF/IFAS. The leaves contain nitrates and oxalates. Boiling and draining removes most of the water-soluble oxalate but not the insoluble part, so boil mature leaves, drain them and discard the water.

Does amaranth come back every year?

It is an annual, so each plant lives one season. NC State lists love-lies-bleeding as an annual; volunteers may appear if seed drops; Adaptive Seeds says love-lies-bleeding occasionally self-seeds.

Sources

1. University of Kentucky Cooperative Extension. Grain Amaranth. Crop profile, issued July 2011 (linked in text)
2. Putnam DH, Oplinger ES, Doll JD, Schulte EM. Amaranth. Alternative Field Crops Manual, University of Minnesota and University of Wisconsin-Madison, November 1989, hosted by Purdue NewCROP (linked in text)
3. Qiu Y, Liu G. Production Guide of Vegetable Amaranth for Florida, HS1407. UF/IFAS Extension, revised February 2024 (linked in text)
4. Ampim PAY, Rivera-Ocasio D. Vegetable Amaranth fact sheet. Prairie View A&M University (linked in text)
5. NC State Extension. Amaranthus caudatus and Amaranthus tricolor. Plant Toolbox; Celosia argentea, Plant Toolbox (linked in text)
6. Santa Fe Botanical Garden. Plant of the Month, March 2023: ‘Hopi Red Dye’ amaranth. visitsfbg.org
7. Cornell University College of Agriculture and Life Sciences. Pigweeds. Weed Ecology and Management profile (linked in text)
8. Kansas State University. Pigweed Identification: A Pictorial Guide to the Common Pigweeds of the Great Plains, S80 (linked in text)
9. Ohio State University Extension. The Pigweed family identification guide, ANR-0077 (linked in text)
10. UC Statewide IPM Program. Pigweeds, Weeds Identification Gallery (linked in text)
11. Pingle U, Ramasastri BV. Effect of water-soluble oxalates in Amaranthus spp. leaves on the absorption of milk calcium. British Journal of Nutrition 1978;40:591 (linked in text)
12. Practical Guide for Saving Seeds from Small Gardens, seed-saving chart; the document names no author (linked in text)
13. Adaptive Seeds. Amaranth, Love Lies Bleeding (Organic) (linked in text) and Amaranth, Rio San Lorenzo (Organic) (linked in text)