Leaf amaranth

Quick facts

Category

leafy greens

Difficulty

beginner

Days to harvest

30 to 50 days

Harvest type

cut leaves, plant regrows for repeated harvests

Spacing

15 cm between plants

Environment

Temperature

20–32°C

pH

5.8 to 7.2

EC (hydroponic)

1.2 to 2 mS/cm

Daily light

18 to 28 mol/m²/day

Climate and zones

USDA zones

9 to 13 (winter low around -7°C or warmer)

Frost tolerance

frost sensitive (dies at first frost)

Season

warm (summer crops, frost-sensitive)

Viable growing environments:

• outdoor in growing season (annual)
• heated greenhouse
• indoor (heated home)
• indoor hydroponics under grow lights

USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.

Growing systems

Leaf amaranth works in:

• deep water culture (rafts)
• media bed (ebb and flow)
• wicking bed
• soil bed

Growing media

The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (leaf amaranth works in the media listed below).

Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.

Nutrient demand by stage

NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.

Aquaponics suitability

Compatible with typical aquaponics nutrient profiles. Fish waste provides enough nitrogen for healthy growth; supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.

Care notes

Excellent hydroponic crop for warm conditions where lettuce and spinach won't grow. EC 1.5-2.5 mS/cm. pH 5.5-6.5. Temperature: 25–35°C (thrives in heat that destroys most leafy greens). Moderate to high light (DLI 15-25 mol/m2/day). Grows fast: baby leaves harvestable in 3-4 weeks from seed, full-sized leaves in 6-8 weeks. Works well in NFT, DWC, and vertical tower systems. Cut-and-come-again harvesting: take outer leaves and the plant continues producing from the center for weeks. Succession planting every 2-3 weeks ensures continuous supply. Nutrient demand is moderate; standard leafy green formula works. The plants bolt (go to seed) eventually but less quickly than lettuce in heat. Amaranth is relatively pest-free in hydroponic systems. The red and purple varieties add visual variety to salad mixes. In aquaponics, leaf amaranth thrives on the warm, nutrient-rich water that tilapia systems produce. One of the most practical warm-climate leafy greens for hydroponic and aquaponic growers. The leaves can be eaten raw in salads when young (baby leaf stage) or cooked like spinach when more mature. Cooking reduces the oxalic acid content. The red and purple varieties (A. tricolor 'Red Stripe', 'Red Leaf') add dramatic color to salad mixes. Amaranth is one of the few leafy greens that actually improves in quality with warm temperatures rather than declining, making it the ideal summer replacement for cool-season greens in hydroponic systems.

Further reading

• Best crops for hydroponic beginners
• The Kratky method: grow lettuce with zero electricity