Root Vegetable

When to Plant Onions in Pennsylvania

The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.

The Short Answer

Pennsylvania is long-day onion territory, and the state's moderate season produces excellent storage onions. The Pennsylvania Dutch tradition of onion growing — including the famous Ebenezer onion set — has deep roots in the state's agricultural heritage.

Pennsylvania Frost Dates

Your planting dates depend on which part of Pennsylvania you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Pennsylvania 5a, 5b, 6a May 5 - May 20 Sep 20 - Oct 5
Central Pennsylvania 5b, 6a, 6b Apr 25 - May 10 Oct 1 - Oct 15
Philadelphia Region 7a, 7b Apr 5 - Apr 20 Oct 15 - Nov 5

Onions Planting Schedule for Pennsylvania

Northern Pennsylvania (Zones 5a, 5b, 6a)

Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Central Pennsylvania (Zones 5b, 6a, 6b)

Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Philadelphia Region (Zones 7a, 7b)

Average last frost: Apr 5 - Apr 20 · Average first frost: Oct 15 - Nov 5

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Growing Onions in Pennsylvania

State-Specific Growing Tips

Plant sets or transplants from early to mid-April. For the largest bulbs, start seed indoors 10-12 weeks before last frost (late January). Long-day onions bulb when days exceed 14 hours in June. Pennsylvania's limestone valley soils grow onions well. In heavier soils, raised beds improve bulb shape and drainage. Cure in a warm, dry, ventilated area for 2-3 weeks.

Recommended Varieties for Pennsylvania

Long-day only: Copra (best storage), Walla Walla (eat fresh), Stuttgarter (from sets), Redwing. Penn State Extension provides variety recommendations.

Common Challenges in Pennsylvania

Onion maggot. Thrips. Botrytis neck rot. Downy mildew in humid conditions.

Growing Tips

Day length triggers bulbing. Northern gardeners need long-day varieties. Southern gardeners need short-day varieties.

Companion Planting

Plant onions alongside these companions for better growth:

Carrots Lettuce Beets Tomatoes

Keep onions away from:

Beans Peas

The Bottom Line

Onions can be grown successfully in Pennsylvania with proper attention to regional frost dates and local growing conditions. Timing varies across the state — Northern Pennsylvania gardeners work with a last frost around May 5 - May 20, while Philadelphia Region sees frost end around Apr 5 - Apr 20. Choose varieties suited to your region, amend your soil based on its specific needs, and monitor for the pests and diseases most common in your area. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Onions Growing Guide National planting guide with all states Pennsylvania Planting Calendar All plants for Pennsylvania Onions in Alabama Alabama planting dates Onions in Alaska Alaska planting dates Onions in Arizona Arizona planting dates Onions in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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