Amaranthus hybridus Seeds | Smooth Amaranth
LATIN NAME: Amaranthus hybridus
COMMON NAME: Smooth Amaranth, Slim Amaranth
Plant Profile
Smooth Amaranth is an erect annual of the Americas, thirty to a hundred and fifty centimetres tall, with long-stalked oval leaves and slender, bristly flower spikes of green to reddish. Like its relatives it is gathered as a cooked green across the warm world, and it is a familiar weed of fields, gardens and roadsides.
It is the wild species closest to the cultivated grain amaranths, and hybrids between them are part of how those crops were shaped. It grows fast in warm, fertile soil, tolerates heat and drought once established, and produces its seed in astonishing quantity. The seed is small, glossy black and produced in such quantity that a single plant can carry half a million grains, which is the root of its weediness.
Science & Biotechnology
Its closeness to the grain amaranths has made it a working species in studies of the crop-weed complex: gene flow runs both ways, and the weed carries useful diversity for crop breeders. It is also a leading case in herbicide-resistance research, with populations resistant to several herbicide groups documented in North American fields since the 2000s.
The C4 photosynthesis that powers its summer growth is the same machinery that makes the grain amaranths productive in heat, and the genus is a standard comparison group in C4 studies. Some populations carry the trichome pattern of the grain amaranths so closely that botanists treat the boundary as a continuum rather than a line.
Uses & Benefits
Where it is not a weed problem its young leaves are a cooked green on the pattern of its relative callaloo, needing only a brief boil; older leaves accumulate oxalates and nitrates and are best avoided. In the garden it can be allowed a corner as a leafy curiosity and pollinator plant.
In farming it is managed rather than grown, and the practical literature on it is about control: rotation, stale seedbeds and timely cultivation. Its brilliance in the autumn border, with deep red selections grown beside it, is why ornamental gardeners tolerate its presence at all. In its native range the plant is also a traditional dye source, the seeds giving a dark red pigment that has been identified in old textile fragments.
Growing from Seed
Sow the fine seed on the surface of warm soil or a free-draining mix in late spring, pressing it in without covering.
Germination takes under a week in warmth of 22 °C or more; the seedlings grow fast and want full sun.
Thin to twenty-five centimetres apart, water in dry spells, and pinch the leading shoots if leafy growth is the object rather than seed; leave a few spikes to ripen if the seed is to be kept. On hot balconies it is one of the few vegetables that relishes the reflected heat, given a deep pot and daily water. The seed ripens over weeks and sheds progressively, so seed savers bag the spikes while green rather than trying to beat the shatter.
Our Take
The wild parent of the grain amaranths: fast, heat-loving and generous with leaves, and a famous weed when it gets the chance, so grow it on purpose or not at all.
Related Reading
More species in the same orbit as Smooth Amaranth: