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

You should be able to estimate when to plant rock cress by using the USDA zone info for Willmar.

Planting Calendar for Rock Cress

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

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

The earliest that you can plant rock cress in Willmar 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 rock cress and expect a good harvest is probably August. Any later than that and your rock cress may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your rock cress indoors.

Last Frost Date

The average date of last frost is May 15 in Willmar. You should expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for Willmar is an average the actual date of last frost is different every year. Since half of the time in Willmar there is a last frost after May 15 be ready to cover your rock cress if you have a surprise late frost.

USDA Zone Info for Willmar

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Willmar

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