Annual Flower

When to Plant Zinnias in Ohio

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

The Short Answer

Zinnias are Ohio's most prolific summer cut flower — the more you cut, the more they bloom, producing armloads of vibrant color from July through the first hard frost.

Ohio Frost Dates

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

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Ohio 5b, 6a May 1 - May 15 Oct 1 - Oct 15
Central Ohio 6a, 6b Apr 20 - May 5 Oct 10 - Oct 25
Southern Ohio 6b Apr 15 - Apr 30 Oct 15 - Oct 30

Zinnias Planting Schedule for Ohio

Northern Ohio (Zones 5b, 6a)

Average last frost: May 1 - May 15 · 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

Central Ohio (Zones 6a, 6b)

Average last frost: Apr 20 - May 5 · Average first frost: Oct 10 - Oct 25

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

Southern Ohio (Zones 6b)

Average last frost: Apr 15 - Apr 30 · Average first frost: Oct 15 - Oct 30

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

Growing Zinnias in Ohio

State-Specific Growing Tips

Direct sow 1 week after last frost when soil reaches 60°F (mid-May). Zinnias grow fast in Ohio's warm, humid summers. Space 9-12 inches apart. Water at the base — overhead watering promotes powdery mildew, which is nearly guaranteed in Ohio's humidity. Deadhead spent flowers or cut stems regularly to encourage continuous blooming.

Recommended Varieties for Ohio

Benary's Giant for large, dahlia-flowered blooms ideal for cutting. State Fair Mix for a range of colors. Queen Lime series for unusual green-tinged blooms. Profusion series for compact bedding.

Common Challenges in Ohio

Powdery mildew is the #1 zinnia problem in Ohio's humid summers — it's cosmetic unless severe but looks unsightly. Choose mildew-resistant varieties. Japanese beetles feed on petals. Alternaria leaf spot 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 Ohio with proper attention to regional frost dates and local growing conditions. Timing varies across the state — Northern Ohio gardeners work with a last frost around May 1 - May 15, while Southern Ohio sees frost end around Apr 15 - Apr 30. 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 Ohio Planting Calendar All plants for Ohio 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

Ready to Start Planting?

Enter your zip code and pick your plant. We'll tell you exactly when to plant, start seeds, and harvest — based on where you live.

Find Your Planting Dates