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

In Naperville you can figure out when to plant cosmos by looking at 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 do well in some cold which tells us that you can plant them slightly earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant cosmos in Naperville 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. Any later than that and your cosmos may not have a chance to really do well. Starting your cosmos indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Naperville. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Naperville may not be accurate from year to year the actual date of last frost changes from year to year. Half of the time in Naperville you get a frost after April 15 so just be sure to be ready to protect your cosmos in the event of one of those late frosts.

USDA Zone Info for Naperville

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 Naperville

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