Onion Seeds,
Ailsa Craig

Start seeds indoors three months before the last expected frost date in spring. Onions begin slowly, so this early start allows for adequate growth before transplanting. Transplant acclimated, stocky seedlings into the garden 4-6 weeks before the last frost of spring, as onions can tolerate light frosts. Since Ailsa Craig is a long-day variety, it is perfect for growers north of the latitude of Saint Louis, Missouri (38.6 degrees N). If you’re not sure how to find your first and last frost dates, consult our blog post 'Our Experts Answer Questions, Share Resources.'

Plant seeds 1/4 inch deep in seed-starting trays and maintain a temperature of around 60 F for germination, which takes 7-14 days. Space seedlings 4-6 inches apart in rows 12 inches apart in the garden. Acclimate seedlings gradually before transplanting outdoors. Make sure that the soil is rich and well-draining to encourage healthy growth.

Feed onions with a balanced fertilizer every 2-3 weeks, as they are heavy feeders. Keep the area weed-free. Water regularly to keep consistent soil moisture but don’t waterlog. When the tops begin to yellow, reduce watering to prepare for harvest.

• Onions will cross with other onions, and occasionally they will cross with scallion types like Welsh onions and Hi Shi Ko bunching onions. Onions will never cross with leeks, chives or garlic.
• If you are growing types that will cross, try to isolate varieties by at least several hundred feet or ideally up to one mile.
• Onions are a biennial seed crop, so you will need to overwinter your first-year roots, ideally by digging them up and storing them for the winter. Replant in early spring, and allow onions to shoot up spikes of purple flowers.
• Let seeds become dry on the plants. Pick seeds when they are hard and dark black, then bring them indoors to finish drying.
• Once dry, separate the seeds from the husks or leave them on and plant them husks and all.