When do you plant onion in zone 5a?

In USDA hardiness zone 5a (last frost ~May 4, 2026, first frost ~Oct 6, 2026): Start seeds indoors Jan 23, 2026–Sep 4, 2026; Start hardening off Apr 3, 2026–Oct 23, 2026; Transplant outdoors Apr 17, 2026–Oct 30, 2026. Exact dates vary by location within the zone.

When to plant onion in zone 5a

A planting schedule for onion in USDA hardiness zone 5a, where the typical last spring frost is around May 4, 2026 and the first fall frost around Oct 6, 2026. Dates are computed from NOAA frost normals for a representative location (Rumford, ME) — your exact dates depend on your address.

Onion planting schedule for zone 5a

Start seeds indoorsJan 23, 2026 – Sep 4, 2026
Start hardening offApr 3, 2026 – Oct 23, 2026
Transplant outdoorsApr 17, 2026 – Oct 30, 2026

Playing it safe with tender crops? Spring frost holds off until about May 15, 2026 in roughly 9 years out of 10.

Want exact oniondates for your address, a drag-and-drop bed layout, and reminders when it’s time to sow? Enter your ZIP:

Free on one garden — no credit card. See the full onion growing guide or the whole zone 5a calendar.

Onion in other zones

More crops for zone 5a

Frost dates are NOAA 1991–2020 climate normals for a representative location (Rumford, ME) in zone 5a; your exact dates depend on your address. Schedules are guidance, not guarantees.