Onion Seeds,
Unzen Early Flat

Unzen Early Flat is a short day onion, meaning it begins forming bulbs when days reach about 10 to 12 hours. It performs best in the South, roughly zone 7 and warmer, sown in late summer to fall and transplanted in winter for a late-spring harvest. Northern gardeners should start seed indoors in midwinter, 10 to 12 weeks before transplanting, and should expect smaller bulbs, as long northern days trigger bulbing early. Seedlings tolerate light frost. 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.'

Sow seeds 1/4 inch deep in seed trays or pots filled with damp potting soil. Maintain a temperature of around 60 F. When transplanting seedlings into the garden, space them 4-6 inches apart in rows 12 inches apart.

Onions are sensitive to weed competition; therefore, keep the planting area weed-free by using straw mulch or hand weeding regularly. Regular watering is very important, especially during dry spells, but avoid waterlogging. Interplanting with cabbage relatives can be beneficial, as sulfur compounds from onions may deter pests.

• 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.