FrostCal

When to Plant Cosmos in Illinois

In a typical Illinois location, start seeds indoors Mar 23 – Mar 30, then sow outdoors Apr 27 – May 11, then transplant outdoors Apr 27 – May 4. Across the state, the outdoor planting window starts as early as Apr 8 in Granite City and as late as May 8 in Roscoe.

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
ChicagoMar 13 – Mar 20Apr 17 – May 1Apr 17 – Apr 24
AuroraMar 22 – Mar 29Apr 26 – May 10Apr 26 – May 3
RockfordMar 27 – Apr 3May 1 – May 15May 1 – May 8
JolietMar 22 – Mar 29Apr 26 – May 10Apr 26 – May 3
NapervilleMar 31 – Apr 7May 5 – May 19May 5 – May 12
PeoriaMar 19 – Mar 26Apr 23 – May 7Apr 23 – Apr 30
SpringfieldMar 18 – Mar 25Apr 22 – May 6Apr 22 – Apr 29
North PeoriaMar 19 – Mar 26Apr 23 – May 7Apr 23 – Apr 30
ElginMar 29 – Apr 5May 3 – May 17May 3 – May 10
WaukeganApr 2 – Apr 9May 7 – May 21May 7 – May 14
ChampaignMar 18 – Mar 25Apr 22 – May 6Apr 22 – Apr 29
CiceroMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
BloomingtonMar 24 – Mar 31Apr 28 – May 12Apr 28 – May 5
Arlington HeightsMar 22 – Mar 29Apr 26 – May 10Apr 26 – May 3
EvanstonMar 29 – Apr 5May 3 – May 17May 3 – May 10
SchaumburgApr 2 – Apr 9May 7 – May 21May 7 – May 14
BolingbrookMar 23 – Mar 30Apr 27 – May 11Apr 27 – May 4
DecaturMar 17 – Mar 24Apr 21 – May 5Apr 21 – Apr 28
PalatineMar 28 – Apr 4May 2 – May 16May 2 – May 9
SkokieMar 29 – Apr 5May 3 – May 17May 3 – May 10
Des PlainesMar 19 – Mar 26Apr 23 – May 7Apr 23 – Apr 30
Orland ParkMar 22 – Mar 29Apr 26 – May 10Apr 26 – May 3
Tinley ParkMar 26 – Apr 2Apr 30 – May 14Apr 30 – May 7
Oak LawnMar 13 – Mar 20Apr 17 – May 1Apr 17 – Apr 24
BerwynMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
Mount ProspectMar 22 – Mar 29Apr 26 – May 10Apr 26 – May 3
NormalMar 28 – Apr 4May 2 – May 16May 2 – May 9
WheatonMar 31 – Apr 7May 5 – May 19May 5 – May 12
Oak ParkMar 14 – Mar 21Apr 18 – May 2Apr 18 – Apr 25
Hoffman EstatesApr 2 – Apr 9May 7 – May 21May 7 – May 14

Showing the 30 most populous of 242 Illinois cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Illinois cities.

Frequently Asked Questions

When should I plant cosmos in Illinois?

In a typical Illinois location, start seeds indoors Mar 23 – Mar 30, then sow outdoors Apr 27 – May 11, then transplant outdoors Apr 27 – May 4. Across the state, the outdoor planting window starts as early as Apr 8 in Granite City and as late as May 8 in Roscoe.

When is the last frost in Illinois?

The average last spring frost in Illinois ranges from April 1 in Granite City to May 1 in Roscoe, 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 Illinois

When to plant cosmos in other states

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