FrostCal

When to Plant Onions in Pennsylvania

In a typical Pennsylvania location, start seeds indoors Feb 9 – Feb 23, then transplant outdoors Mar 23 – Apr 6. Across the state, the outdoor planting window starts as early as Mar 2 in Philadelphia and as late as Apr 17 in Hermitage.

Method Start indoors, then transplant
Days to maturity 90–120 days

Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Onions Planting Dates by City

CityStart indoorsTransplant
PhiladelphiaJan 19 – Feb 2Mar 2 – Mar 16
PittsburghFeb 13 – Feb 27Mar 27 – Apr 10
AllentownFeb 9 – Feb 23Mar 23 – Apr 6
ErieFeb 15 – Mar 1Mar 29 – Apr 12
ReadingFeb 3 – Feb 17Mar 17 – Mar 31
ScrantonFeb 12 – Feb 26Mar 26 – Apr 9
BethlehemFeb 9 – Feb 23Mar 23 – Apr 6
BensalemFeb 10 – Feb 24Mar 24 – Apr 7
LancasterFeb 8 – Feb 22Mar 22 – Apr 5
AbingtonJan 31 – Feb 14Mar 14 – Mar 28
LevittownFeb 10 – Feb 24Mar 24 – Apr 7
HavertownJan 19 – Feb 2Mar 2 – Mar 16
HarrisburgFeb 4 – Feb 18Mar 18 – Apr 1
AltoonaFeb 14 – Feb 28Mar 28 – Apr 11
YorkFeb 15 – Mar 1Mar 29 – Apr 12
State CollegeFeb 9 – Feb 23Mar 23 – Apr 6
Wilkes-BarreFeb 12 – Feb 26Mar 26 – Apr 9
NorristownJan 28 – Feb 11Mar 11 – Mar 25
ChesterJan 19 – Feb 2Mar 2 – Mar 16
Mount LebanonFeb 7 – Feb 21Mar 21 – Apr 4
Bethel ParkFeb 7 – Feb 21Mar 21 – Apr 4
WayneJan 28 – Feb 11Mar 11 – Mar 25
RadnorJan 28 – Feb 11Mar 11 – Mar 25
WilliamsportFeb 14 – Feb 28Mar 28 – Apr 11
MonroevilleFeb 11 – Feb 25Mar 25 – Apr 8
Cranberry TownshipJan 28 – Feb 11Mar 11 – Mar 25
Drexel HillJan 22 – Feb 5Mar 5 – Mar 19
PlumFeb 5 – Feb 19Mar 19 – Apr 2
Back MountainFeb 12 – Feb 26Mar 26 – Apr 9
EastonFeb 7 – Feb 21Mar 21 – Apr 4

Showing the 30 most populous of 121 Pennsylvania cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Pennsylvania cities.

Frequently Asked Questions

When should I plant onions in Pennsylvania?

In a typical Pennsylvania location, start seeds indoors Feb 9 – Feb 23, then transplant outdoors Mar 23 – Apr 6. Across the state, the outdoor planting window starts as early as Mar 2 in Philadelphia and as late as Apr 17 in Hermitage.

When is the last frost in Pennsylvania?

The average last spring frost in Pennsylvania ranges from March 30 in Philadelphia to May 15 in Hermitage, based on NOAA 1991–2020 climate normals.

How long do onions take to grow?

Onions typically take 90–120 days from planting to harvest. Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Other Crops in Pennsylvania

When to plant onions in other states

Related Guides