When to plant onions in Montana

Plant out in Billings

Mar 23–Apr 13

Across Montana the window opens between March 23 and May 2. Find your city below; the dates follow each town's own average last frost.

Start indoors, Billings: Feb 9–Mar 9
Plant out, Billings: Mar 23–Apr 13
Last frost, Billings: May 4

Start seeds indoors 8–12 weeks before the last frost; plant out 3–6 weeks before the last frost. Northern gardens need long-day varieties and southern gardens need short-day ones. A wrong pick gives small bulbs.

Onions planting dates by city

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost

JanFebMarAprMayJunJulAugSepOctNovDec

BillingsMar 23–Apr 13

MissoulaMar 29–Apr 19

Great FallsMar 25–Apr 15

BozemanApr 14–May 5

Butte-Silver BowMay 2–May 23

HelenaMar 28–Apr 18

KalispellApr 19–May 10

Questions

When should I plant onions in Montana?

In Billings, plant out from March 23 to April 13. Across Montana the window opens between March 23 and May 2, depending on the local last frost.

How is this date worked out?

Start seeds indoors 8–12 weeks before the last frost; plant out 3–6 weeks before the last frost. Frost dates are NOAA 1991–2020 averages for the weather station nearest each city.

More for Montana

Onions in other states

Frost dates for every city in Montana