By mid-summer the red amaranth in Steve's garden is in glorious full bloom.
We aren't exactly sure which species of Amaranthus we have growing here in our Zone 8 garden, but our best guess is A. tricolor, a species that is grown widely in Southeast Asia for its edible leaves, and grown widely everywhere else as an ornamental. Chinese spinach is a very variable erect annual, cultivars of which range from 2 to 5 ft (60-150 cm) in mature height. Leaf color is also variable, including various shades of red, green, bronze, yellow and gold. The form we are growing here in Florida (let's call it red amaranth) gets 5 ft (150 cm) high and has burgundy red leaves and produces lots of branches that terminate in plumes of burgundy red flowers. In different parts of the world, different cultivars are preferred for food. There also are numerous ornamental cultivars selected for leaf and flower color. 'Joseph's Coat' has leaves that combine dark green, red, golden yellow and brown.
Location Amaranthus tricolor is probably native to Southeast Asia and possibly Africa as well. It is widely planted in the tropics for food, and in the tropics and subtropics as an ornamental.
Culture Light: Grow amaranth in full sun. Moisture: Amaranth likes a well drained soil and can tolerate moderate drought. Hardiness: USDA Zones 7-10. Chinese spinach is an annual, but it needs a fairly long growing season to mature and produce seeds. If you just want the colorful and tasty leaves for salads or cooking "greens", you should be able to get a crop in zone 6. The plants do best in hot climates, and thrive during hot summers. Propagation:Amaranthus species tend to be weedy, and most reseed themselves joyfully. We don't know who did the counting, but it is reported that a single plant can produce 100,000 seeds. We planted some seeds of red amaranth in the vegetable garden about 15 years ago and we haven't replanted since. Baby amaranths pop up faithfully throughout the spring and summer, and we decide, based on location, which plants will be allowed to mature and which will add to the mulch.
This young amaranth flower stalk in late spring will mature to produce tens of thousands of (edible) seeds in the fall.
Here in Florida, we use young Chinese spinach leaves in fresh garden salads. They have a nice distinctive, earthy taste and certainly add color. Elsewhere, millions of people eat the leaves like spinach: steamed or lightly stir fried. They are often added to soups. The leaves are high in protein, calcium, iron and vitamins A and C. In late summer the plants produce gobs of seeds, but we have yet to try roasting them. The ornamental cultivars are used in beds and borders and especially valued in arrangements because the flowers last a long time.
The Incas in South America, grew Amaranthus caudatus (what they called quihuicha and what we call Inca wheat) for the grain-like seeds, which were ground into flour, or simply roasted until they popped like popcorn. (Today, selections of A. caudatus for the ornamental garden are called love lies bleeding or tassel flower.) Once a staple on the Incan table, quihuicha (also spelled kiwicha) fell out of use after the Spanish conquest, but is now enjoying a comeback. It turns out the abundant amaranth seeds are among the most nutritious foods known. They have a higher concentration of protein than any of the true cereal grains (i.e. members of the Poaceae such as wheat, corn, rice, etc.). Not only that, amaranth seeds have an amino acid makeup that is more nearly perfect for human nutrition than any other grain. The Aztecs in Mexico had their own grain amaranth too: A. hypochondriacus, and it too was relegated to the history books because of Spanish disapproval. (Perhaps the Spanish were wary of hypochondriacs?)