To start amaranthus seeds indoors using soil blocks, begin by creating blocks from a well-draining seed-starting mix. Place 1-2 seeds per block, pressing them gently into the surface and covering lightly, as amaranthus seeds need some light to germinate. Keep the soil blocks moist and maintain a temperature of 70-75°F; the seeds should sprout in 10-14 days. Once the seedlings have grown a few sets of leaves, thin them to one seedling per block. About a week before transplanting outdoors, harden off the seedlings by gradually exposing them to outdoor conditions, starting with indirect sunlight and increasing exposure daily.

After the risk of frost has passed and the soil has warmed to at least 60°F, transplant the seedlings into a sunny, well-draining spot in the garden, spacing them 6-12 inches apart. Water thoroughly to help them settle into their new environment.

Once established, amaranthus is relatively low-maintenance. Water regularly, especially during dry periods, but avoid overwatering. Pinch back the growing tips to encourage bushier growth and more blooms. Fertilize lightly with a balanced fertilizer if the soil is poor, though amaranthus generally thrives without heavy feeding.

Amaranthus blooms from summer through fall and can be harvested at any stage for fresh bouquets or left to dry for dried arrangements. Cut stems in the morning or evening when the temperatures are cooler and immediately place them in water.

To dry amaranthus, start by harvesting the blooms when they are fully mature and vibrant, typically in late summer or early fall. Cut the stems long enough to handle, and remove any excess foliage. Bundle the stems together and hang them upside down in a cool, dry, and well-ventilated area away from direct sunlight. You can use a paper bag or netting to cover the bundles and protect them from dust and pests. Allow the amaranthus to dry for about 1-2 weeks or until the blooms are crispy and the stems snap easily. Once dry, store the amaranthus in airtight containers or jars to keep them fresh for use in arrangements and crafts.