Plant Amaranthus in a sunny, sheltered spot with well-drained, fertile soil. It thrives in rich, moisture-retentive ground, so dig in organic matter before planting to improve soil structure.
Space plants about 30-45cm (12-18in) apart to allow good air circulation and give the tall, branching stems room to grow. Water regularly during dry spells and apply a mulch to help retain soil moisture and suppress weeds. Deadheading is not essential, but removing spent flowers can tidy the plant and may prolong blooming.
In exposed sites, staking may be needed to support the long, drooping tassels, especially in windy weather. Feed occasionally with a balanced liquid fertiliser to encourage strong growth and vivid colour. Treat it as a half-hardy annual, lifting and composting after the first frosts.