Onion Types

Modern cultivated types of onion fall into two main groups - the common onion and aggregatum group.

Common onions constitute the vast majority of commercial crops and form single bulbs. They include common, dry bulb onions, and salad and pickling onions.

Bulb shape, color and leaf characteristics vary markedly within this group. In practice they are categorized according to the daylength needed to stimulate bulb development. There are the short ones (12-13 hours) and the intermediate or long (14-16 hours) daylength varieties. 

Types include "Sweet Onions", "Spanish Onions" and "Dutch Onions".

Aggregatum onions form clusters of bulbs and include shallots, which have pods similar to garlic and reddish brown skin surrounding a bulb that has subtle flavors of both garlic and onion.

Shallots have a very high dry matter content - between 16 and 35% - compared to 7-15% for onions.