Planting & Growing Instructions for Heirloom / Open Pollinated Onions

Heirloom Onion Seed

(Allium cepa)

Onion varieties are daylength sensitive: Short-day varieties do best in thWalla Walla Onion - St. Clare Heirloom Seedse South, Long-Day varieties in the North, and Intermediate-day length varieties can do well in both.

Heirloom / Open Pollinated Onion seeds like fertile, well-drained soil and can be either direct seeded as soon as the soil can be worked or greenhouse started in flats. Start indoors plant  in pots or flats 8-10 weeks before last frost, ⅛ – ¼” deep, 2-4 seeds per inch. Set out or thin to about 3-5” apart. Keep seedlings cut back to about 3” until transplanting to strengthen seedling. Can set out transplants once the soil can be worked, about 4 weeks before the last frost. Outdoors, plant at same depthWhite Sweet Spanish Onion - St. Clare Heirloom Seeds and rate, in rows 12-24” apart, as soon as soil can be worked. Onion seedlings are fairly cold-tolerant so they will survive in the soil in cold weather as long as the ground doesn’t freeze.  Germination will occur in 6-16 days in soil 60-75°F with optimum germination temperature at 70°F. Plant Onion Seeds in full sun. Harvest when tops dry  and fall over. Cure in dry place for 2-4 weeks.