Purus frumentum Seeds | Purus Grain
LATIN NAME: Purus frumentum
COMMON NAME: Purus Frumentum, Small Grain
Plant Profile
The defining trait is the fruitcase, a hard, bony glume that clasps each kernel and protects it but also locks it away from easy eating. In maize the fruitcase was selected away so the grain stands free; in teosinte it remains, and the ear shatters so the seeds scatter. The paired, one-seeded cupules sit along a fragile rachis, and the whole spike is small enough to miss in a field of taller grasses. This armour is the central puzzle of maize domestication.
The leap from teosinte to maize turns out to rest on a small set of genes. Two loci above all mark the change: teosinte branched1 (tb1), which controls whether the plant makes many side branches or a single stalk with a central ear, and teosinte glume architecture1 (tga1), which governs the hard fruitcase around the kernel. A change at tga1 alone is enough to free the grain from its stony coat, a striking example of how few steps separate a wild grass from a crop.
The question of how maize arose was a famous dispute. George Beadle argued that maize descended from teosinte through a handful of gene changes, the mutation view, and backed it with crosses showing the two were essentially one species. Paul Mangelsdorf countered with a tripartite hybrid theory in which maize came from a cross involving a now-extinct wild relative, not teosinte directly. Modern genetics sides with Beadle: teosinte is the wild parent, and the differences are few and strong.
Because teosinte is the close wild kin of maize, its gene pool is a reservoir for traits the crop may need, from pest resistance to stress tolerance, and living stands are protected as genetic heritage in Mexico. The plants are gathered and banked as seed rather than farmed, and the wild populations are watched as climate and land use press on their thin valley habitats. Losing them would mean losing options for the crop’s future.
Science & Biotechnology
A wild teosinte plant branches freely and bears many small ears rather than one big one, and each ear carries only a handful of kernels. Despite the distance in form, it crosses with maize and the hybrid is fertile, so genes flow both ways where the two grow together; this is why teosinte is a living laboratory for studying the crop rather than a closed wild species. The cross also lets breeders move traits such as disease resistance into maize.
The seed is a small store of starch and oil like any grass grain, and the yellow types carry zeaxanthin, the carotenoid that also colours maize and that is studied for eye health. The wild grain is hard and low yielding, so it is not a food crop, but the seed fraction is sampled in genetic collections for its diversity of storage proteins and pigments. The leaf, like maize, runs the C4 pathway and is efficient in heat and bright light.
Uses & Benefits
Space rows forty to fifty centimetres apart, and if you are saving seed, grow teosinte at a distance from any maize planting so pollen from the crop does not cross the stand; a few hundred metres and a tall barrier crop help. Harvest the slender ears once the glumes turn straw-coloured and the kernels are hard, then thresh out the grain from the fruitcases and dry it before storage.
Growing from Seed
Teosinte looks nothing like the maize it spawned. Where corn carries hundreds of naked kernels on a fat cob, teosinte hides each seed inside a stony casing and spaces them in slender, branching spikes, so that a single wild ear may hold fewer grains than a pinch. Yet under the skin the two are close enough to cross and yield fertile young, which is why teosinte sits at the heart of every story about how people turned a weedy grass of Mexican valleys into the world’s staple cereal. A note on names: seed catalogues once listed this plant as Purus frumentum, a label with no standing in plant nomenclature, which is why the page link still carries that old word.
Grow teosinte as you would a short-season maize: it wants warmth, sun and a fine seedbed, and it is best kept apart from maize if you want pure seed. The seed is small and the seedlings are grassy and easy to mistake for a weed, so label the row. Sow after the soil is warm and keep the stand clean until it is established.
Sow the seed one to two centimetres deep in a warmed, well-worked bed and keep it moist until emergence; the first leaves are narrow grass blades and the plant tillers as it grows. Thin the seedlings to about twenty centimetres apart once they hold four true leaves so the branches have room, and water through dry spells. The plant reaches a metre or so and flowers in a single flush.
Our Take
For grass-family neighbours worth growing alongside, look at Sorghum bicolor and the wild Setaria viridis, and for a pasture grass in the same family try Paspalum notatum; none is a maize parent, but all show how varied the cereals are.
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