Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. 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 Chicago can be reffered to in order to figure out when it's possible to plant primula.

Planting Calendar for Primula

Frost tolerance for primula:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Since primula are very cold tolerant you can plant them a lot earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant primula and expect a good harvest is probably September. You probably don't want to wait any later than that or else your primula may not have a chance to fully mature. You can get started a few weeks earlier by starting your primula indoors.

Last Frost Date

The average date of last frost is April 15 in Chicago. It might get as low as -10°F during the coldest months of winter.

Always keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Chicago and it is different every year. Half of the time in Chicago last frost occurs after April 15 so be sure to be ready to cover your primula in the event of a late frost.

USDA Zone Info for Chicago

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Chicago

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