How can I successfully grow large onions in pots?

To successfully grow large onions in pots, choose a pot that is at least 10-12 inches deep and fill it with well-draining soil. Plant onion sets or seedlings about 1 inch deep and 4-6 inches apart. Water regularly, ensuring the soil is consistently moist but not waterlogged. Place the pot in a sunny location and fertilize every few weeks with a balanced fertilizer. Harvest when the tops have fallen over and dried out.