Amaranth

Sow after the last frost, once soil reaches 70 F

Wait until all danger of frost has passed and the soil has warmed to 70 F, then sow seed only an eighth to a quarter inch deep into a fine, firm, well-drained bed, in rows 12 to 18 inches apart. Keep the surface evenly moist until the seedlings are up, which takes about a week at 70 to 75 F. Amaranth is a warm-season annual with no frost tolerance at all, and germination slows badly or fails outright once soil is below 50 F. The seed is tiny and the seedlings are fragile, so a crusted or dried-out surface will thin the stand before it ever establishes.

Set greenhouse transplants about 3 weeks from sowing

Sow 2 seeds per cell a quarter inch deep in a well-drained mix. Seedlings emerge in 2 to 3 days, are ready to harden off within 2 weeks, and can go to the field about 3 weeks from sowing. Set them 12 inches apart in rows 24 inches apart, and wet and fertilize the holes just before planting. Amaranth seedlings grow slowly for their first month even though they germinate fast, so in a short season that month is dead time. Starting under cover buys it back, and it sidesteps the poor field stands that the tiny seed so often gives.

Mulch and cultivate early - no herbicide can rescue this crop

Mulch around transplants, or cultivate and hand weed until the plants stand 10 to 12 inches tall, after which they shade out later-emerging weeds on their own. Choose a bed that is not already carrying a heavy pigweed or lambsquarters population. Amaranth grows slowly for its first month and simply loses to weeds during that window. It is also a close relative of pigweed, waterhemp and Palmer amaranth, so the herbicides that would clear those weeds injure the crop right along with them.

⚠ No herbicides are registered for use on amaranth in the US. Cultivation, mulch and hand weeding are the only legal options - do not reach for a pigweed product.

Nitrogen before planting, then sidedress on a schedule

Incorporate compost plus a complete N-P-K fertilizer before planting, then sidedress with N-P-K at about 10, 20 and 30 days after transplanting. Let a soil test set the actual rate rather than a default - compost or a cover crop will reduce what the crop needs. Amaranth is a low-management crop that will grow in poor soil, but it responds well to fertilizer, and a leaf crop that gets cut repeatedly draws on that feeding to power each regrowth. Note that UF/IFAS reports fertilizer has not been shown to dramatically increase yields, so treat the schedule as a ceiling, not a target.

⚠ Do not push inorganic nitrogen past the soil test recommendation. UF/IFAS HS1407 warns that excess inorganic nitrogen fertilization might result in a pale leaf and toxic nitrate accumulation in the plants - the very leaves you are eating.

Thin seedlings to 6 inches apart

Sow with about an inch between seeds, then once the seedlings are a few inches tall thin the stand to roughly 6 inches apart, in rows 12 to 18 inches apart. Amaranth is seeded far heavier than the final stand because the dust-fine seed establishes unevenly. Opening the canopy back up keeps air moving through the planting, which matters because stem rot or wet rot (Choanephora cucurbitarum) is the main fungal disease of concern and it runs through crowded, humid stands.

Scout for blister beetles, webworm, tarnished plant bug and flea beetles

Walk the planting through summer and check growing tips and leaves for striped amaranth beetle, tarnished plant bug (Lygus), flea beetle, amaranth weevil, blister beetles and alfalfa webworm. Hand pick what you find, strip damaged leaves, and pull plants that are badly infested. Rotate the crop and clear debris rather than counting on a rescue treatment. Blister beetles and alfalfa webworm are the ones documented to cause economic losses (in Missouri); the rest mostly chew foliage. A crop grown for grain tolerates considerable insect leaf feeding without affecting yields, so chewed leaves alone are not a reason to act. Few diseases cause serious losses either.

⚠ No synthetic insecticides are labeled for this crop and no fungicides are labeled for use on amaranth - do not apply any pesticide whose label does not name this crop. Various organic compounds can be used. Low pest pressure plus the absence of registered synthetics is exactly why amaranth is a good candidate for organic production.

Cut greens at 6 inches, and stop once it flowers

Start cutting once plants reach a height of 6 inches or more; early varieties are ready as soon as one month after planting. Either cut about 3 inches above the ground so the plant regrows, or pull the entire plant with roots. Repeat cuts as the plant recovers, and cool the leaves to 45 to 55 F before delivery to hold quality. Per UF/IFAS, once the plant begins flowering the leaves become fewer and are not suitable for harvest, and repeated cutting both keeps new leaves tender and delays that bolt. Amaranth carries a greens harvest through the heat that has already finished off spinach and lettuce.

Take grain after a killing frost, once a dry week has cured it

Let the heads ripen and wait for a killing frost, then give the crop about a week of good drying weather before harvesting. Rub or thresh the heads over a tarp, winnow the seed in a breeze, clean the plant trash and foreign material out of the grain, and dry it below about 11 percent moisture before storing. Handle the heads gently - shattering during cutting is where the seed is lost. Amaranth does not dry down far enough on its own to thresh cleanly and there are no approved desiccants for it, so the killing frost plus a dry week is what kills and cures the plant. If stems and leaves are still wet the seed turns sticky and smears through the equipment, and plant trash left mixed in the seed is what raises the chance of molding in storage.