Annual Flower

When to Plant Zinnias in Pennsylvania

The cut-and-come-again champion. The more you cut zinnias, the more they bloom. A cottage garden essential.

The Short Answer

Zinnias are Pennsylvania's summer cut flower workhorse — fast, productive, and available in every color. Pennsylvania flower farms feature them prominently at farmers markets.

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

Zinnias 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
4 wks before frost
Transplant Outside
1 wks after frost
Direct Sow
1 wks after frost

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

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

Start Seeds Indoors
4 wks before frost
Transplant Outside
1 wks after frost
Direct Sow
1 wks after frost

Philadelphia Region (Zones 7a, 7b)

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

Start Seeds Indoors
4 wks before frost
Transplant Outside
1 wks after frost
Direct Sow
1 wks after frost

Growing Zinnias in Pennsylvania

State-Specific Growing Tips

Direct sow from mid-May. Space 9-12 inches in full sun. Water at base. Cut or deadhead regularly for continuous bloom through frost.

Recommended Varieties for Pennsylvania

Benary's Giant, State Fair, Queen Lime, Profusion. Penn State Extension includes zinnias in annual flower recommendations.

Common Challenges in Pennsylvania

Powdery mildew in humid summers. Japanese beetles on petals. Alternaria in wet conditions.

Growing Tips

Water at the base to prevent powdery mildew. Cut flowers just above a leaf node to encourage more branching and blooms.

Companion Planting

Plant zinnias alongside these companions for better growth:

Tomatoes Peppers

The Bottom Line

Zinnias 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

Zinnias Growing Guide National planting guide with all states Pennsylvania Planting Calendar All plants for Pennsylvania Zinnias in Alabama Alabama planting dates Zinnias in Alaska Alaska planting dates Zinnias in Arizona Arizona planting dates Zinnias 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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