Onions are grown in several ways and for different uses. A main distinction is made between seed onion and onion set for cultivation, and also between store and bunching onion production. They are grown at a density of 80-100 plants per m². Many different varieties or types for different cultivation times, cultivation methods and uses are available. Seed onions are challenging due to their extremely long germination and juvenile phase, in which the plants are sensitive and easily out-competed. This is avoided by setting the onions, but the suitability for storage suffers and the cost of sets are higher. Too high quantities of nitrogen can increase the susceptibility to diseases. Dry storage and a low fungal infection pressure during harvesting are optimal for a good shelf life. Drying costs can be reduced if post-harvest ripening (curing) in the field is possible for several days before collection.