Onion is a diverse agricultural crop that is classified into groups based on response to day-length. Onions form bulbs in response to a critical day-length and are classified as short-, intermediate-, and long-day types. Bulbs also vary in color (red, yellow, and white) (Fig. 7.1), shape (flat, globe, grano, torpedo), flavor (sweet or pungent), and market use (fresh, storage and processing). Most onion varieties grown in Utah are long-day, pungent, storage types that respond favorably to local growing conditions.
Selection of appropriate onion varieties for a location and market is an important decision. There are numerous onion varieties available and seed companies introduce new ones each year. Some varieties commonly grown in Utah include ‘Calibra’, ‘Candy’, ‘Charismatic’, ‘Crockett’, ‘Delgado’, ‘Desperado’, ‘Granero’, ‘Joaquin’, ‘Legend’, ‘Maverick’, ‘Mesquite’, ‘Ranchero’, ‘Redwing’, ‘Sedona’, ‘Swale’, ‘Tequila’, and ‘Vaquero’.
USU Extension conducts field trials to evaluate onion varieties under local conditions. Data is gathered on yield quantity and quality, timing of crop maturity, pest tolerance, and storage quality (extension.usu.edu/productionhort/htm/vegetables/