Annual Flower

When to Plant Cosmos in Missouri

Delicate, daisy-like blooms that dance in the breeze. Cosmos thrive in poor soil and practically grow themselves.

The Short Answer

In Missouri, plant cosmos based on your regional frost dates. Northern Missouri has a last frost around Apr 20 - May 5, while Southern Missouri sees frost end around Apr 1 - Apr 15. Continental climate. Hot, humid summers. Four seasons. Good growing season in most of state.

Missouri Frost Dates

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

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

Cosmos Planting Schedule for Missouri

Northern Missouri (Zones 5b, 6a)

Average last frost: Apr 20 - May 5 · 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 Missouri (Zones 6a, 6b)

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 Missouri (Zones 6b, 7a)

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

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

Growing Cosmos in Missouri

Cosmos in Missouri's Climate

Cosmos are the zero-effort flower. Direct sow from mid-May. No fertilizer, no fussing, no deadheading necessary (though it helps). They grow 3-5 feet tall and self-seed prolifically. Perfect for filling unused garden edges with color and pollinator habitat.

Soil Considerations for Missouri

Rich loess soils along Missouri River. Rocky Ozark soils in south. Heavy clay common. Generally fertile. Make sure soil has warmed to at least 60°F before planting cosmos outside.

Missouri Climate & Growing Season

Continental climate. Hot, humid summers. Four seasons. Good growing season in most of state. Cosmos 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 Missouri: Northern Missouri (5b, 6a) has a last frost around Apr 20 - May 5, while Southern Missouri (6b, 7a) sees frost end around Apr 1 - Apr 15. This difference matters for cosmos — transplant timing shifts by several weeks across the state.

Growing Tips

Don't over-fertilize — rich soil produces more leaves and fewer flowers. Let some flowers go to seed for next year's crop.

Companion Planting

Plant cosmos alongside these companions for better growth:

Tomatoes Squash

The Bottom Line

Cosmos can be grown successfully across Missouri, but your exact planting dates depend on which region you're in. Northern Missouri gardeners should plan around a Apr 20 - May 5 last frost, while those in Southern Missouri can typically plant earlier. For exact dates based on your zip code, use our free planting date finder.

Related Guides

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