One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Platteville should be looked at to figure out when it's the best time to plant cosmos.

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 very little cold which means 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 Platteville 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 fully mature. Starting your cosmos indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Platteville. In the coldest months of winter you can expect an average low temperature of -20°F.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Platteville and it can change quite a bit from year to year. Half of the time in Platteville you get surprised by a frost after April 15 so be sure to be ready to protect your cosmos in the event of a late frost.

USDA Zone Info for Platteville

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Platteville

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