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.

A common way of estimating when it's the best time to plant cosmos is to use the USDA zone info for Marseilles.

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 a tiny bit of cold which tells us that you can plant them a bit earlier in the year than other frost tender plants.

The earliest that you can plant cosmos in Marseilles 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. If you wait any later than that and your cosmos may not have a chance to fully mature. Starting your cosmos indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In Marseilles the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

Remember that the actual date of last frost is an average because it is based on the USDA zone info for Marseilles and it changes from year to year. Half of the time in Marseilles last frost occurs after April 15 so be sure to be ready to cover your cosmos if you have a late frost.

USDA Zone Info for Marseilles

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 Marseilles

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