FrostCal

When to Plant Cosmos in Washington

In a typical Washington location, start seeds indoors Feb 24 – Mar 3, then sow outdoors Mar 31 – Apr 14, then transplant outdoors Mar 31 – Apr 7. Across the state, the outdoor planting window starts as early as Mar 8 in Port Townsend and as late as Jun 6 in Cheney.

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
SeattleFeb 13 – Feb 20Mar 20 – Apr 3Mar 20 – Mar 27
Tri-CitiesMar 30 – Apr 6May 4 – May 18May 4 – May 11
SpokaneMar 29 – Apr 5May 3 – May 17May 3 – May 10
TacomaFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
VancouverMar 1 – Mar 8Apr 5 – Apr 19Apr 5 – Apr 12
BellevueFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
KentFeb 20 – Feb 27Mar 27 – Apr 10Mar 27 – Apr 3
EverettFeb 24 – Mar 3Mar 31 – Apr 14Mar 31 – Apr 7
RentonFeb 13 – Feb 20Mar 20 – Apr 3Mar 20 – Mar 27
Federal WayFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
Spokane ValleyMar 29 – Apr 5May 3 – May 17May 3 – May 10
YakimaApr 10 – Apr 17May 15 – May 29May 15 – May 22
KirklandFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
BellinghamMar 4 – Mar 11Apr 8 – Apr 22Apr 8 – Apr 15
KennewickFeb 28 – Mar 7Apr 4 – Apr 18Apr 4 – Apr 11
AuburnFeb 20 – Feb 27Mar 27 – Apr 10Mar 27 – Apr 3
PascoFeb 28 – Mar 7Apr 4 – Apr 18Apr 4 – Apr 11
MarysvilleFeb 24 – Mar 3Mar 31 – Apr 14Mar 31 – Apr 7
RedmondFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
LakewoodFeb 11 – Feb 18Mar 18 – Apr 1Mar 18 – Mar 25
OlympiaApr 1 – Apr 8May 6 – May 20May 6 – May 13
ShorelineFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
RichlandMar 9 – Mar 16Apr 13 – Apr 27Apr 13 – Apr 20
South HillMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
SammamishFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
BurienFeb 2 – Feb 9Mar 9 – Mar 23Mar 9 – Mar 16
LaceyApr 1 – Apr 8May 6 – May 20May 6 – May 13
City of SammamishMar 2 – Mar 9Apr 6 – Apr 20Apr 6 – Apr 13
BothellFeb 8 – Feb 15Mar 15 – Mar 29Mar 15 – Mar 22
EdmondsFeb 9 – Feb 16Mar 16 – Mar 30Mar 16 – Mar 23

Showing the 30 most populous of 133 Washington cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Washington cities.

Frequently Asked Questions

When should I plant cosmos in Washington?

In a typical Washington location, start seeds indoors Feb 24 – Mar 3, then sow outdoors Mar 31 – Apr 14, then transplant outdoors Mar 31 – Apr 7. Across the state, the outdoor planting window starts as early as Mar 8 in Port Townsend and as late as Jun 6 in Cheney.

When is the last frost in Washington?

The average last spring frost in Washington ranges from March 1 in Port Townsend to May 30 in Cheney, 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 Washington

When to plant cosmos in other states

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