✔The best time for planting onion seeds outdoors is in spring, as soon as the soil can be worked in your area. Place them about an inch (2.5 cm.) deep in the soil and approximately half an inch (1.5 cm) or more apart. If planting rows, space them at least one and half to two feet (45 – 61 cm) apart.
✔When it comes to onion seed germination, temperature plays an active role. While typically germination occurs within 7-10 days, soil temperature affects this process.
✔Once seedlings have sufficient leaf growth, thin them down to around 3-4 inches (7.6 to 10 cm) apart. Transplant onion seedlings that were started indoors about 4-6 weeks before the last expected frost or freeze date, provided the ground is not frozen.
✔Onion plants have shallow roots and require frequent irrigation throughout the growing season.