Growing onions in zone 5
Bulbing is triggered by day length: long-day varieties for the North, short-day for the South, intermediate in between — the wrong type simply won’t bulb. Sets are easiest; transplants give bigger bulbs.
Zone 5 covers southern New England, Great Lakes, Iowa, Nebraska, Colorado Front Range — a classic four-season garden climate with room for spring and fall plantings. Zone dates are medians: frost timing varies within a zone with elevation and terrain, so treat these windows as a solid default and refine them with your own city’s dates below.
Make it local
These windows use zone 5's typical frost dates (last frost ~Apr 22, first frost ~Oct 12). For windows computed from your frost dates, run the ZIP code frost lookup and open the planting calendar — it remembers your city. The seed starting scheduler turns the whole seed rack into one printable, date-sorted list.
Frequently asked questions
When do I plant onions in zone 5?
Transplant Mar 11 – Mar 25, counted from zone 5's typical last frost around Apr 22. As a hardy crop it tolerates the light frosts on either side of that window.
When should I start seeds indoors for onions in zone 5?
Sow indoors Feb 11 – Feb 25 — that's 10 to 8 weeks before the typical Apr 22 last frost, giving sturdy transplants exactly when the garden is ready for them.
Can I direct sow onions in zone 5?
Yes — direct sow Mar 25 – Apr 8. Transplants buy a head start, but direct-sown plants catch up quickly once soil warms.