One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

One way of estimating when it's the best time to plant rock cress is to check out the USDA zone info for Iron Mountain.

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 do well in cold you can plant them much earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant rock cress in Iron Mountain 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 really do well. You can get started a little bit earlier by starting your rock cress indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Iron Mountain. It might get as low as -30°F during the coldest months of winter.

It's important to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Iron Mountain and it changes from year to year. Half of the time in Iron Mountain last frost occurs after May 15 so be sure to be ready to cover your rock cress in the event of a late frost.

USDA Zone Info for Iron Mountain

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Iron Mountain

You may be interested in your other planting guides for Iron Mountain.