Onion Sweet Spanish Seeds produce reliable, uniform crops with a mild, sweet flavor. These onions store well and reach 30cm (12") in size. Sow in fertile, well-drained soil, 1.5cm deep in rows 30cm apart, after the last spring frost. Germination takes 14-28 days, with regular watering during dry spells. For earlier harvest, start indoors 8-10 weeks before the last frost, harden off, and transplant 25cm apart.