The foxtail amaranth (Amaranthus caudatus L.) is one of the most popular species of domesticated amaranths. It has been cultivated for a long time as a multipurpose pseudocereal of high nutritive value, as a vegetable and as an ornamental plant (eFloras, 2021). It belongs to the group of grain amaranths, along with Amaranthus cruentus and Amaranthus hypochondriacus (Brenner et al., 2000). The plant residue after grain harvest may be fed to livestock or used for thatching.
Morphology
Amaranthus caudatus is an annual erect herb 0.5-1.5 (-2.5) m in height, commonly reddish or purplish in colour. The root system consists in a short enlarged taproot and secondary roots that explores deeper soil layers (NRC, 1989). The stem is rather stout, moderately branched, glabrous or thinly furnished with rather long hairs. The leaves are simple and entire, spirally arranged, borne on petiole up to 8 cm long shorter than the blade. The leafblade is broadly ovate to rhomboid-ovate or ovate-elliptical, 2.5-15 (-20) cm long × 1–8 cm broad, glabrous or sparsely hairy below, pinnately veined. The inflorescence is large (0.9 to 1.5 m), robust, and complex, consisting of numerous agglomerated cymes arranged in axillary and terminal spikes, the terminal one drooping or nodding. The inflorescence is showy, very versatile in colour, ranging from red, purple to white and less often green, silvery green or yellow. It may look like a red cat's tail, hence one of its vernacular name: "cat's tail" or "red-hot-cattail". The flowers are unisexual, sessile: the male flowers are mostly at the apex of the spike. The fruits are ovoid-globose, one-seeded capsules, about 1.5-2.5 mm long, almost smooth or slightly furrowed, abruptly narrowed to a short thick beak. The seeds are nearly globose, 1-1.5 mm long, very light, smooth and shining, very variable in colour, from ivory, yellowish white to reddish brown or dark brown (eFloras, 2021; Agong, 2006; NRC, 1989). The 1000-seed weight is 0.5-1.1 g (Agong, 2006)
Uses
Amaranthus caudatus is mainly used as a source of food in India and South America (Agong, 2006). Known as kiwicha in Peru, its seeds are reported to be flavourful and highly nutritious and, unlike quinoa, do not contain saponins. The seeds are used to feed infants and pregnant women, disabled and elderly people (NRC, 1989). They can be used in several recipes. They produce a crunchy nutty "popcorn" when heated, they can be used as a snack, as a cold cereal with milk and honey, in sweets, or as a “breading” on chicken or fish. The grain can be ground into flour, rolled into flakes, "puffed", or boiled for porridge. The flour can be blended with cereal flours to improve their nutritive value (higher protein, better amino acid balance and higher vitamin content). It enters in bakery specialties. In Ethiopia, foxtail amaranth seeds are considered a famine food in times of scarcity, and combined with teff to make injera flatbread in times of abundance (Agong, 2006).
The plant contains pigments that can be used for food colouring. Young leaves and stems of foxtail amaranth can be boiled as greens, like spinach (NRC, 1989). Although they are not reported in statistics, the various amaranths may actually be the most widely grown vegetable crop in the humid tropics (NRC, 1989). After grain harvest, the stover can be fed to livestock or used for thatching. Feed uses of the stover been reported in South America and in other countries such as China (NRC, 1989; Brenner et al., 2000). All parts of foxtail amaranth have ethnomedicinal applications and have been reviewed for their potential benefits (anti-diabetic, anti-hyperlipidemic, anti-atherogenic, regulator of arterial pressure, cardioprotective) in human health (Martinez-Lopez et al., 2020; Agong, 2006).
