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 mid to 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.
For successful seed harvest, start seeds very early in a coldframe or hoophouse 3/1 (so that seeds mature before weather is too hot). Minimum population size: 20 (plants are unisexual so only the female plants will produce seed) so grow at least 60 plants. Ideal isolation distance: 2 miles – just make sure your neighbors are not letting their spinach flower. Remove plants that are weak and the 1st 10% of plants that bolt. When most seeds are tan, collect seeds by clipping stems and drying them. Clean by stripping seeds off stems & winnowing.