Grow your own leeks from seed and taste the difference, pure natural from organically grown parent stock. Leeks are a good source of potassium, folic acid, and vitamins A & C. They also have antibacterial and anti-fungal properties. Top Tips: Try salad leeks as a milder alternative to spring onions in summer; Earthling up plants for traditional leeks to blanch the stems is important to keep them tender for winter use.