How to Grow Amaranth in Australia

Amaranth (Amaranthus tricolor) is a fast-growing leafy annual in the amaranth family, Amaranthaceae, grown for its tender green, red or bicoloured leaves and shoot tips. Sold as Chinese spinach, en choy or callaloo, it keeps cropping through the summer heat that sends English spinach to seed. The usual mistake is sowing the tiny seed too early, into soil still too cold to wake it.

Three mistakes that matter

1. Sowing into cold soil. Amaranth is a tropical plant. Seed in cold soil comes up slowly or not at all, and frost kills seedlings outright. Wait for warm soil, at the times in When to plant.
2. Sowing too deep or too thick. The seed is about 1 mm across, with roughly 900 to the gram, so a heavy hand buries it or crowds the row. Mix it with sand, sow 3 to 6 mm deep and thin early.
3. Letting plants flower and seed. Once flower spikes form, plants make fewer leaves, and dropped seed can turn amaranth into a garden weed. Pinch out spikes as they appear, which keeps plants low and bushy, and pull plants before any seed ripens.

When to plant

Sow once the soil holds at least 18°C and the last frost has passed. Seed germinates fastest above 20°C, slows sharply in cooler soil and can fail below 10°C. Sow a short row every three to four weeks for a steady supply of young leaves.

At the cool edge of the window, start seed in punnets indoors and plant out after the last frost. At the late edge, shortening days push amaranth to flower early, so pick those rows young.

Site, soil and setup

Amaranth copes with poorer ground than most leafy greens, but fertile soil grows bigger, more tender leaves.

Container growing

A pot at least 30 cm across, holding about 13 L, grows a few plants for regular picking. Fill it with premium potting mix and sow any leaf type, such as 'Green Leaf', 'Red Leaf' or 'Bicolour'. Pick often so plants stay bushy.

• Water: check daily in summer and water before the mix dries. See watering pots in summer.
• Feed: fish and seaweed blend at 25 mL per 9 L fortnightly. A controlled release fertiliser for containers, mixed in at sowing, can replace it.
• Position: full sun; move the pot into light afternoon shade during heatwaves.

Sowing Seeds

Sow direct into warm soil, or start in punnets where the frost-free season is short.

Sowing direct

• Mix the seed with a little dry sand or fine compost so it spreads thinly. See sowing tiny seeds.
• Sow 3 to 6 mm deep, a seed every 2.5 cm or so, in rows 30 to 45 cm apart.
• Keep the surface damp; seedlings usually appear in 7 to 14 days.
• Thin as set out in Thinning once seedlings are big enough to handle.

Starting in punnets

In Canberra, Tasmania and the tablelands, a start under cover adds weeks of picking to a short summer.

• Sow a pinch of seed per cell of seed-raising mix at the same depth, then thin each cell to the strongest seedling.
• In a cool room, a seedling heat mat speeds germination.
• Transplant while seedlings are young and only after the last frost, since older transplants can flower prematurely.
• Harden off (accustom seedlings to sun and wind over about a week) before planting out 15 cm apart.

The varieties below are all leaf types of Amaranthus tricolor, and leaf colour is the main difference between them. Grain amaranth and love-lies-bleeding (Amaranthus caudatus) are grown for seed and flowers instead.

Care by growth stage

Warmth and steady water decide this crop: dry soil pushes it into early flower, and cold nights stall it. Weeks count from sowing.

Heavy nitrogen feeding can leave the leaves pale and loaded with nitrate, so use balanced feeds like those above rather than a high-nitrogen side-dressing.

Thinning

Thinning gives each plant room to branch and lets air move through the row, which helps prevent rots.

• Thin in two steps as seedlings grow, using the thinnings as baby greens.
• Finish at about 15 cm apart for rows picked young and often.
• Leave 30 to 50 cm between plants kept for months of picking, because they grow large.
• Snip unwanted seedlings at soil level so the keepers' roots stay undisturbed.
• Pinch out the main growing tip once plants are growing strongly, so they branch.

Companion planting

A tall row of amaranth shades its neighbours through summer, which suits some crops and crowds others.

Grows well with

• Silverbeet, which appreciates afternoon shade from taller plants in hot climates.
• Lettuce, which holds up better in partial shade through the warm months.

Keep apart

• Pigweed and other wild amaranths, which host beet webworm and share the crop's pests.
• Any crop already infested with beet webworm, such as beans or beetroot, since the caterpillars move to nearby hosts.

Harvesting Leaves

Start picking once plants are growing strongly with several full-sized leaves, usually 4 to 8 weeks from sowing.

• Pull whole young plants at about four weeks for the most tender greens.
• For repeat picking, cut the top shoots and young leaves, leaving the lower leaves to regrow.
• Pick again about two weeks later, as new shoots form.
• Pick in the cool of the morning, because the leaves wilt quickly.

Wrap the damp stems in plastic and refrigerate them; the leaves keep for up to 2 days. Steam or stir-fry leaves and shoot tips briefly, until just wilted, and expect red types to tint the cooking water.

Young leaves can go raw into a salad in small amounts. The leaves and stems contain oxalate and nitrate, which cooking reduces. For a larger serve, boil them and throw the water away, which removes the soluble oxalate. Anyone prone to kidney stones should ask their doctor how much is sensible.

Common problems

Flowering while small. Shortening days in late summer and autumn, and dry soil at any time, push amaranth into flower early. Keep the soil moist and pinch spikes (see Three mistakes), and outside the tropics sow from spring to early summer.

Patchy germination. Poor germination is common with amaranth, often because the surface dried out or the soil was cold. Keep the seedbed damp until seedlings emerge, and resow gaps; for depth, see Three mistakes.

Yellowing and collapse in wet soil. Water standing in the root zone rots the roots. Drain heavy soil as in Site, soil and setup, and ease off watering through wet weather.

Seedlings everywhere the next summer. These come from plants left to drop seed (see Three mistakes); hoe them out while they are small. Amaranth may be an environmental weed in some areas, so check your council's weed list before planting.

Pests and diseases

Check shoot tips and leaf undersides every few days, and use only sprays and baits labelled for the pest, keeping to the withholding period.

Beet webworm (Spoladea recurvalis). Green caterpillars about 2 cm long web leaves together or roll them, feeding inside and eating windows through the leaf. Numbers can build after rain, when weedy hosts such as pigweed flourish. Squash larvae inside rolled leaves, remove webbed leaves, and if numbers climb, spray a Bt (Bacillus thuringiensis) caterpillar spray, which works only once eaten.

Aphids (family Aphididae). Small sap-suckers that cluster on shoot tips and leaf undersides in some seasons. Hose colonies off, or spray insecticidal soap straight onto them every few days. Read more

Common garden snail (Cornu aspersum) and slugs. Both chew small seedlings overnight. Hunt by torch after rain or watering, and if a bait is needed, choose an iron-based one. Read more

Damping off (Pythium and Rhizoctonia species). Seedlings rot and collapse at soil level soon after emerging, worst in cold, wet or overwatered soil. Sow into warm, free-draining soil and water lightly until seedlings establish. Read more

Prevention first

• Pull pigweed and other wild amaranths from around the patch.
• Water at the base early in the day, keeping the leaves dry.
• Space plants as in Thinning, so air moves through the row.
• Remove spent plants and fallen debris after the last picking.

Tips

1. Sow amaranth as the last English spinach finishes in spring. Spinach bolts in summer heat, while amaranth thrives in it, so the two share one bed across the year.
2. Red and bicolour types double as bedding colour among flowers and vegetables.
3. Recipes are easy to find under its other names: en choy in Chinese stir-fries, callaloo in Caribbean soups and vleeta in Greek boiled greens.