Plan your onions (bulbing) planting around local frost risk and soil temperature, then work backward from the harvest week your buyers need. The calendar below is a starting point, not a field-level weather forecast.
Madison WI, Des Moines, southern MN, central MI. Average last spring frost May 8, first fall frost September 29 — a 144-day frost-free season.
Windows are calculated from your zone's average frost dates. Adjust ±1 week for microclimates, elevation, and your own frost records.
Southeast growers must plant short-day varieties. Long-day types will make tops but never bulb below 36° latitude.
Plant near: carrots, beets, lettuce
Keep away from: beans, peas
BAU Farm Intelligence turns these windows into per-field tasks — indoor seed-start reminders, transplant dates, harvest projections — using your farm's actual frost history.