Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first chance to plant cosmos in Romeoville can be estimated by reviewing the USDA zone info.

Planting Calendar for Cosmos

Frost tolerance for cosmos:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Cosmos tend to make it in some cold which tells us that you can plant them a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant cosmos in Romeoville is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant cosmos and expect a good harvest is probably August. You probably don't want to wait any later than that or else your cosmos may not have a chance to really do well. If you are starting your cosmos indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Romeoville the average date of last frost happens on April 15. It might get as low as -15°F during the coldest months of winter.

Just be sure to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Romeoville and it changes from year to year. Half of the time in Romeoville you get surprised by a frost after April 15 so be sure to be ready to cover your cosmos if you have a surprise late frost.

USDA Zone Info for Romeoville

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Romeoville

You may be interested in your other planting guides for Romeoville.