Onion crop. Flowering crop of onions, Allium cepa, grown in a field. This particular crop is grown for its commercial seed and hence the large flower heads. Onions are exploited for their underground bulbs which can be eaten raw or cooked. They are a good source of vitamin B2 (riboflavin) and calcium. Onion crops are grown in temperate and subtropical regions around the world. Photographed in France.