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

By using the USDA zone info for Naperville it's a good idea to estimate when you can plant purple rock cress.

Planting Calendar for Purple Rock Cress

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

Purple Rock Cress do well in a bit of cold which tells us that you can plant them a lot earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant purple rock cress 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 purple rock cress and expect a good harvest is probably September. If you wait any later than that and your purple rock cress may not have a chance to fully mature. Starting your purple rock cress indoors is a great way to get them started a few weeks earlier.

Last Frost Date

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

Keep in mind 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 purple rock cress in the event of a surprise 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.