Before planting it is a good idea to find your USDA Zone info to determine 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.

By reviewing the USDA zone info for Naperville it's possible to determine when you can plant primula.

Planting Calendar for Primula

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

Primula can survive in pretty solid cold which tells us that you can plant them quite a bit earlier in the year than other frost tender plants.

The earliest that you can plant primula in Naperville 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 grow to maturity. You can get started a little bit earlier by starting your primula indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Naperville. It might get as low as -15°F during the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Naperville and it will vary from year to year. Since half of the time in Naperville you get a frost after April 15 be ready to cover your primula if you have a late frost.

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.