Annual Flower

When to Plant Cosmos in Rhode Island

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

The Short Answer

In Rhode Island, plant cosmos based on your regional frost dates. Maritime climate moderates temperatures. Four seasons. Moderate growing season. Ocean influence reduces frost risk near...

Rhode Island Frost Dates

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

Region	Zones	Last Frost (Spring)	First Frost (Fall)
Rhode Island	6a, 6b, 7a	Apr 15 - May 5	Oct 5 - Oct 25

Cosmos Planting Schedule for Rhode Island

Rhode Island (Zones 6a, 6b, 7a)

Average last frost: Apr 15 - May 5 · Average first frost: Oct 5 - Oct 25

Start Seeds Indoors

4 wks before frost

Transplant Outside

1 wks after frost

Direct Sow

1 wks after frost

Growing Cosmos in Rhode Island

Cosmos in Rhode Island'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 Rhode Island

Rocky, acidic New England soils. Sandy near coast. Glacial deposits throughout. Amendment needed for most vegetable gardening. Make sure soil has warmed to at least 60°F before planting cosmos outside.

Rhode Island Climate & Growing Season

Maritime climate moderates temperatures. Four seasons. Moderate growing season. Ocean influence reduces frost risk near coast. Cosmos cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.

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 Rhode Island, but your exact planting dates depend on which region you're in. Rhode Island gardeners should plan around a Apr 15 - May 5 last frost, while those in Rhode Island can typically plant later. For exact dates based on your zip code, use our free planting date finder.

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