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.

A common way of determining when to plant purple rock cress is to look at the USDA zone info for Chicago.

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.

Since purple rock cress are one of those plants that can tolerate quite a bit of cold weather you can plant them much earlier in the year than more sensitive plants.

The earliest that you can plant purple rock cress 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 purple rock cress and expect a good harvest is probably September. Any later than that and your purple rock cress may not have a chance to really do well. If you are starting your purple rock cress indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Chicago. In the coldest months of winter you can expect an average low temperature of -10°F.

Keep in mind that USDA zone info for Chicago is just an average and the actual date of last frost will vary from year to year. Half of the time in Chicago last frost occurs after April 15 so just be sure to be ready to cover your purple rock cress if you have a surprise 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.