Onion planting depth depends on the type of onion material you use:
- Onion sets (small dormant bulbs): Plant them about 1 to 2 inches (2.5 to 5 cm) deep, with the pointed tip facing up. The tip should be just below or barely showing above the soil surface. Plant sets 2 to 4 inches apart for bulbs, or closer if harvesting green onions. Avoid planting sets too deep as it can inhibit bulb development
- Onion seeds: Sow seeds about ½ inch (1.3 cm) deep in loose soil. Thin seedlings to 3 to 4 inches apart once they grow
- Onion transplants: Plant with about 1 inch (2.5 cm) of the lower plant portion buried in soil. Roots should be trimmed to about 2 inches and tops to about 4 inches before planting
In summary, planting onion sets about 1 to 2 inches deep is standard, with the tip just under or slightly above soil level. Seeds go about ½ inch deep, and transplants about 1 inch deep. Proper spacing and soil preparation also help onions grow well
