Amaranthus retroflexus Seeds | Redroot Pigweed
LATIN NAME: Amaranthus retroflexus
COMMON NAME: Redroot Pigweed
Plant Profile
The stem base flushes dull red and the taproot below shares that colour, which is where the common name redroot comes from. From that base a single annual stem rises to well over a metre in a warm season, branching near the top into a dense, bristly panicle. The leaves are oval, softly hairy on the underside and carried on long stalks, and the whole plant is coated in a fine mealy wax that helps it shrug off drought.
Redroot pigweed is often confused with vegetable amaranth and with Powell amaranth, but the reflexed spike tip, the mealy stem and the paired terminal spines at the leaf base are its own. Grain types such as Amaranthus tricolor and Amaranthus caudatus hold their flowers in looser, drooping tassels and lack the tight reflexed hook, so the panicle shape alone is usually enough to tell them apart in the field.
The red colour of the stem is not anthocyanin but a betacyanin called amaranthin, the same class of pigment that tints beetroot and cactus flowers. In redroot amaranth the pigment concentrates in the leaf axils and the young stems, and its presence is one reason the plant was once gathered as a food colouring. Betacyanins also mark the species as a member of the centrosperm group rather than a true carotenoid-coloured leafy green.
Redroot amaranth asks for almost nothing: scatter the seed on bare, firm soil in full sun and keep the surface from crusting. It is a C4 plant using the NAD-malic-enzyme pathway, so it keeps growing through heat that stalls most leafy greens, and a single plant will shed an enormous number of seeds across a long flowering stretch.
If you grow it for greens, pinch the central spike as it forms so the plant pumps energy into side leaves instead of seed. For seed saving, cut the panicle once the lower grains feel hard and dry it on a sheet, then rub the chaff free by hand.
Science & Biotechnology
Because redroot pigweed thrives on disturbed ground and resists herbicides, it has become a model for studying weed adaptation. Research lines have sequenced its plastid genome and tracked the spread of herbicide-resistance traits across farmland populations, and the plant’s flexibility in leaf shape and flowering time is now textbook material for anyone studying how a casual coloniser turns into a dominant arable weed.
Uses & Benefits
A single bent hair on the top of the flower spike is the whole reason this plant carries the name retroflexus. Each slender branch of the inflorescence ends in a tip that curls back on itself, reflexed like a small hook, and a botanist who first described the species in the eighteenth century saw that reflex and recorded it in the Latin. Most gardeners never notice it because the plant is written off as a weed, yet the same curled tip is a reliable field mark that separates it from the upright grain amaranths sold as vegetables.
The foliage carries oleanolic-acid saponins and, on nitrogen-rich soil, can build up enough nitrate to harm livestock that eat large amounts at once. That chemistry is why agronomists treat the leaves as a useful but cautious fodder: the young shoots are nutritious, yet a field grown on heavy fertiliser needs testing before it is cut for animal feed.
The leaves up to the first flowering are mild enough to stand in for spinach in a quick wilt, and they keep their colour after cooking because of the betacyanin. Older leaves grow a hairy surface and a sharper bite, so the harvest window matters more than any recipe: pick low, pick young, and the pigweed on the path edge becomes dinner.
The thousands of tiny seeds on one panicle are edible and were ground into a flour by several Indigenous groups, but the grain is so small and the chaff so plentiful that the plant never joined the cultivated grain amaranths as a field crop. It remains a wild harvest rather than a managed one, which is exactly the gap that separates pigweed from its tasselled vegetable cousins.
Growing from Seed
Long before it was a weed of the row crop, redroot amaranth was a famine food across the Americas, boiled like spinach and dried for winter. Markets in West Africa and South Asia still sell the young tops as a cooked green, and the same plants that volunteer in a vegetable bed can be thinned and eaten rather than composted.
Sow thick and thin to one sturdy seedling every fifteen centimetres once the third true leaf has opened; crowding simply feeds the weed habit. Because emergence is uneven, judge the thinning by leaf number on the strongest seedling in each clump rather than by any fixed date.
Our Take
Redroot amaranth is the easiest amaranth to meet and the hardest to keep out of the bed, so treat it as a borrowed crop rather than a permanent one. If you want a leafy amaranth you actually planted, the broad coloured types such as Amaranthus tricolor and the spiny-stemmed spiny amaranth are cleaner to manage, and the old-world potherb epazote (Chenopodium ambrosioides) shares the same love of poor, sunny ground. Save a corner for the volunteer pigweed, but don’t let it write next year’s garden for you.
Related Reading
If Redroot Pigweed appeals to you, these related plants are worth a look: