When to Plant Flower Seeds in Iowa?

In Iowa, cold winter and early spring temperatures keep many flower seeds from germinating outdoors until late spring or summer. Start flower seeds indoors or wait until later in the growing season, when daytime temperatures average 70 degrees F, to sow flower seeds directly in the garden.

Fast-Growing Flowers

• Flowers that grow quickly, such as sunflowers and zinnias, should be planted after the last average frost date in mid-May, depending on your location in Iowa. Other examples of flowers to plant at this time include nasturtium and cosmos.

Slow-Growing Flowers

• Plant flowers that grow more slowly indoors, about eight weeks before the last frost date. This means mid-March for many flowers, such as snapdragons and impatiens. Some flowers grow even more slowly and should be started 10 to 12 weeks before planting, such as vincas and geraniums.

Tip

• Provide proper growing conditions for seeds started indoors, recognizing the importance of lighting for germination. Some seeds require light for germination, meaning they should be pressed in the soil but left uncovered. Most seeds germinate within two weeks when properly maintained.