Oilseeds
Crops grown for the oil stored in their seed. The grouping is defined by the end use and spans unrelated families — Brassicaceae, Asteraceae, Fabaceae, Pedaliaceae, Euphorbiaceae — which is why it explains nothing botanical and a great deal commercially.
An agricultural grouping. Not a taxon and not claimed to be one — cereals span two families, pulses and oilseeds overlap, and the grouping is about what the crop is grown for.
Two products from one seed
Crushing an oilseed produces oil and meal, and both are sold. The meal is usually the larger fraction by weight and is a protein feed in its own right, so an oilseed crop is priced against two markets at once and a crusher’s margin sits between them. That is structurally different from a cereal, where there is one product.
Fatty acid composition is the specification
What distinguishes one oilseed from another commercially is the fatty acid profile, not the oil percentage. High-oleic types are bred for frying stability, high-linolenic types for drying oils and paints, and castor for a hydroxy acid nothing else supplies. A buyer specifies composition, and a grower is contracted against it.
Food and non-food are different crops in the same group
Several members are not food crops at all. Castor and jatropha are industrial feedstocks with toxic seed or meal, and treating them as edible oilseeds is a category error with a safety dimension. The grouping is about where the value is stored, not about what may be eaten.
Small seeds, shallow sowing, uneven ripening
Most oilseeds are small-seeded relative to cereals and are sown shallow into a fine seedbed, and many are indeterminate enough that pods or capsules ripen in sequence. Shattering losses at harvest are consequently a defining problem of the group, and desiccation or swathing is common where the plant will not ripen evenly on its own.
Oil is a store, and stores degrade
Seed oil oxidises, and the more unsaturated the profile the faster. Storage moisture and temperature therefore govern quality after harvest as much as the crop did before it, and free fatty acid rises in poorly stored seed long before anything is visible.
What this is not
- Pulses are legumes grown for the dry seed itself rather than for its oil, and their rotational value is nitrogen rather than a second product.
- Industrial crops overlap here: castor and jatropha appear in both because the grouping is by use and a crop can have two.