When to plant onions in New Hampshire

Onions
Plant out in Manchester
Mar 19–Apr 9

Across New Hampshire the window opens between March 18 and April 2. Find your city below; the dates follow each town's own average last frost.

Start indoors, Manchester
Feb 5–Mar 5
Plant out, Manchester
Mar 19–Apr 9
Last frost, Manchester
Apr 30

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
ManchesterMar 19–Apr 9
NashuaMar 18–Apr 8
ConcordMar 27–Apr 17
DoverMar 22–Apr 12
RochesterMar 19–Apr 9
KeeneApr 2–Apr 23
PortsmouthMar 23–Apr 13
DerryMar 19–Apr 9

Questions

When should I plant onions in New Hampshire?

In Manchester, plant out from March 19 to April 9. Across New Hampshire the window opens between March 18 and April 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 New Hampshire

Onions in other states

Frost dates for every city in New Hampshire