Annual Flower

When to Plant Zinnias in Delaware

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

The Short Answer

In Delaware, plant zinnias based on your regional frost dates. Northern Delaware has a last frost around Apr 10 - Apr 25, while Southern Delaware sees frost end around Apr 1 - Apr 15. Moderate climate with maritime influence. Good growing conditions for a wide range of vegetables.

Delaware Frost Dates

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

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Delaware 7a Apr 10 - Apr 25 Oct 10 - Oct 25
Southern Delaware 7b Apr 1 - Apr 15 Oct 20 - Nov 5

Zinnias Planting Schedule for Delaware

Northern Delaware (Zones 7a)

Average last frost: Apr 10 - Apr 25 · 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 Delaware (Zones 7b)

Average last frost: Apr 1 - Apr 15 · Average first frost: Oct 20 - Nov 5

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

Growing Zinnias in Delaware

Zinnias in Delaware's Climate

Your warm, humid summers grow zinnias prolifically. Direct sow from mid-May. Powdery mildew is the main issue in humid conditions — water at the base, never overhead, and choose mildew-resistant varieties. Cut or deadhead regularly for continuous bloom through frost.

Soil Considerations for Delaware

Sandy soils in south, clay loam in north. Generally well-drained. Slightly acidic. Make sure soil has warmed to at least 60°F before planting zinnias outside.

Delaware Climate & Growing Season

Moderate climate with maritime influence. Good growing conditions for a wide range of vegetables. Zinnias cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.

Growing season length varies across Delaware: Northern Delaware (7a) has a last frost around Apr 10 - Apr 25, while Southern Delaware (7b) sees frost end around Apr 1 - Apr 15. This difference matters for zinnias — transplant timing shifts by several weeks across the state.

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 across Delaware, but your exact planting dates depend on which region you're in. Northern Delaware gardeners should plan around a Apr 10 - Apr 25 last frost, while those in Southern Delaware can typically plant earlier. 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 Delaware Planting Calendar All plants for Delaware 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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