Onion Seeds,
Stuttgarter

Start seeds indoors three months before the last expected frost date in spring. Transplant acclimated, stocky seedlings into the garden 4-6 weeks before the last frost of spring, as onions can tolerate light frosts. As a long-day onion, it bulbs best in northern regions where summer daylength reaches 14 to 16 hours. If you’re not sure how to find your area's day length or 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 or directly in the garden after the danger of frost has passed. Germination usually takes 7-14 days when soil temperatures are around 60 F. Space seedlings 4-6 inches apart, with 12 inches between rows, and amend the soil with organic compost to encourage healthy growth.

Feed with a balanced fertilizer or compost tea every 2-3 weeks. Keep the soil consistently moist but avoid waterlogging, which can cause rot. Use mulch to maintain soil moisture and suppress weeds. When the tops start to yellow and fall over, stop watering to allow the bulbs to cure before harvesting.

• 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.