Choose a site in full sun. Spread 6 inches of fine textured compost on top of the ground and work it into the top 12 inches of soil with a tiller or turning fork. Rake smooth, and break up any clods. The seeds are tiny, so the soil texture needs to be as fine as possible.
Plant the African spinach seeds after all danger of frost has passed. Spread the seeds thinly across the top of the soil and press in lightly. Water with a fine spray of water daily until sprouts appear. Thin the amaranth plants to 2 feet apart after they develop three full sets of leaves.
Begin fertilizing the African spinach plants monthly with a balanced granular or liquid fertilizer with minor elements when they are 6 inches tall. Water regularly to promote better growth, although amaranth is drought tolerant.
Check frequently for insects, including tarnished plant bug, flea beetle and amaranth weevil. Treat plants with an organic insecticide according to label directions for leaf vegetables.
Cut leaves from the plants as desired, leaving enough to enable them to continue growing. Pinch out the tops of branches to encourage bushiness.