Amaranth plants grow well in average to rich, well-draining soil with equal amounts of nitrogen and phosphorus. Like many vegetable crops, they need at least five hours of sunlight a day to do well. While they grows best in moist but well drained soil, they will tolerate somewhat dry soil too. Amaranth seeds are very fine, so generally, the seeds are sprinkled over a prepared area after the risk of last frost has passed. Amaranth seeds can be started indoors as well about three to four weeks before the last frost date. Once the amaranth seeds have sprouted, they should be thinned to about 18 inches (46 cm.) apart.