FrostCal

When to Plant Cosmos in Rhode Island

In a typical Rhode Island location, start seeds indoors Mar 14 – Mar 21, then sow outdoors Apr 18 – May 2, then transplant outdoors Apr 18 – Apr 25. Across the state, the outdoor planting window starts as early as Apr 14 in Newport and as late as May 8 in Narragansett.

Method Direct sow
Days to maturity 60–90 days

Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early.

Cosmos Planting Dates by City

CityStart indoorsDirect sowTransplant
ProvidenceMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
WarwickMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
CranstonMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
PawtucketMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
East ProvidenceMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
WoonsocketMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
CoventryMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
CumberlandMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
North ProvidenceMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
South KingstownApr 3 – Apr 10May 8 – May 22May 8 – May 15
West WarwickMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
JohnstonMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
North KingstownMar 30 – Apr 6May 4 – May 18May 4 – May 11
NewportMar 10 – Mar 17Apr 14 – Apr 28Apr 14 – Apr 21
BristolMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
SmithfieldMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
LincolnMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
Central FallsMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
WesterlyMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
PortsmouthMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
MiddletownMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
BarringtonMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
NarragansettApr 3 – Apr 10May 8 – May 22May 8 – May 15
East GreenwichMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
Newport EastMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
Valley FallsMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
WarrenMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
North SmithfieldMar 25 – Apr 1Apr 29 – May 13Apr 29 – May 6
North ScituateMar 28 – Apr 4May 2 – May 16May 2 – May 9

Showing the 29 most populous of 29 Rhode Island cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Rhode Island cities.

Frequently Asked Questions

When should I plant cosmos in Rhode Island?

In a typical Rhode Island location, start seeds indoors Mar 14 – Mar 21, then sow outdoors Apr 18 – May 2, then transplant outdoors Apr 18 – Apr 25. Across the state, the outdoor planting window starts as early as Apr 14 in Newport and as late as May 8 in Narragansett.

When is the last frost in Rhode Island?

The average last spring frost in Rhode Island ranges from April 7 in Newport to May 1 in Narragansett, based on NOAA 1991–2020 climate normals.

How long do cosmos take to grow?

Cosmos typically take 60–90 days from planting to harvest. Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early.

Other Crops in Rhode Island

When to plant cosmos in other states

Related Guides