The "five grains" of the ancients usually means rice, two kinds of millet, wheat and beans.
Tips
culture
The list differs between sources; another common version has 麻 'hemp' in place of 稻 'rice'. The word lives on in 五谷丰登 'a bumper harvest', a New Year wish, and 五谷不分 'can't tell one grain from another', said of someone who knows nothing of farm work.