How to grow amaranth: Most gardeners grow amaranth from seed sown outside directly in the ground.
Sow amaranth seeds 0.6 inches (1.4 cm) deep. Optimal soil temperature for germination is between 60.3°F (15.7°C) and 68.9°F (20.5°C). Seeds will germinate in 5-10 days.
Amaranth requires 65-70 days to be ready for harvest from seed, depending on the amaranth variety and the weather during the growing season.
Optimal day air temperature for growing amaranth is between 70.4°F (21.3°C) and 72.8°F (22.7°C). Optimal night temperatures are between 68°F (20°C) and 69.8°F (21°C). Amaranth can endure air temperatures as low as 59°F (15°C) during the night and up to 80.6°F (27°C) during the day.
Soil temperature during amaranth growth should be between 70°F (21.1°C) and 75°F (23.9°C) in optimal conditions, but can withstand soil temperatures as low as 50°F (10°C).
Required soil pH for amaranth growth is 5.5-7.0 but the optimal pH is 6.0-6.9.
Optimal sunlight for amaranth is 6-12 hours per day. Amaranth should be watered between 1.0-1.1 inches (2.6-2.7 cm) of water per week, adjusting for weather conditions and type of soil accordingly.
Amaranth spacing: When planting amaranth seeds directly into the ground sow seeds 0.6 inches (1.4 cm) deep spaced 9 inches (22.8 cm) apart with rows spaced 12 inches (30.5 cm) apart.
How to grow amaranth in your garden: Many gardeners grow amaranth for their sprouts. In this case there is no need for seed spacing or row spacing as most will be harvested before plant matures.
Amaranth seeds are also grown and harvested as greens. Select those amaranth varieties that are suitable for greens! It is recommended to apply more nitrogen and phosphorous when growing amaranth greens. When harvesting cut 2-3 inches above ground level. Assuming optimal growing conditions are maintained plant will continue to grow more greens.
For amaranth seed or grain allow the plant to flower and reach maturity. The seeds or what is referred to as amaranth grain is within the flower, so harvest carefully.