Your onion transplants need to get nice and big before planting outside ASAP in early spring. Start seeds inside in late January under high quality grow lights. Use a good seed starting mix (we recommend Vermont Compost’s Fort Light). Ideal temperature for germination is 70-80° (use heating mat). Days to germination: 4-13. Once leaves appear, grow plants at 70° - 75°. Fertilize weekly with fish/kelp fertilizer. Harden off plants before planting into fertile garden soil 1” deep, spaced 4” apart in rows 15” apart. Mulch with straw, keep well watered and weeded.
Harvest in late July once plants have turned brown, but while stems and skins are still intact. Dig on a dry day & cure for a week in a warm dry place with good air circulation.
Onions are a difficult seed saving crop because they are biennial. Minimum population size: 25. Dig & cure onions as you would for eating selecting the best for seeds. Store over onions at cool temp (35°-40°) with 65-70% humidity. Plant in mid spring spaced 4” apart in rows 28” apart. Clip seed stalks into a bucket as pods mature (late summer). Dry, thresh, and winnow to clean.
Our Recommendations with Rossa Di Milano Organic Onion
