The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

By referring to the USDA zone info for Lewiston you should be able to determine when it's possible to plant rock cress.

Planting Calendar for Rock Cress

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

Rock Cress do well in cold which tells us that you can start planting them much earlier than more sensitive plants.

The earliest that you can plant rock cress in Lewiston 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 rock cress and expect a good harvest is probably September. If you wait any later than that and your rock cress may not have a chance to fully mature. 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 April 15 in Lewiston. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Lewiston is not always accurate the actual date of last frost will vary from year to year. Half of the time in Lewiston you get surprised by a frost after April 15 so make sure that you are prepared to protect your rock cress if you have a surprise late frost.

USDA Zone Info for Lewiston

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 Lewiston

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