Sweet onions are flatter ... are partially due to how they're grown. Spanish onions are grown in low-sulfur soil, contributing to the lack of astringent taste and the slight hint of sweetness.

For long-day length onions, which have more time to grow leaves to produce bulbs, choose varieties like 'Early Yellow Globe,' 'Ebenezer,' and 'White Sweet Spanish' onions. Most long-day onions are ...