One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. 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 nierembergia is to use the USDA zone info for Caribou.

Planting Calendar for Nierembergia

Frost tolerance for nierembergia:	Not tolerant of frost.
When to plant:	After the last frost has passed.

Since nierembergia require warm weather you have to wait until after the last frost has passed before you can plant them.

The earliest that you can plant nierembergia in Caribou is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant nierembergia and expect a good harvest is probably August. Any later than that and your nierembergia may not have a chance to fully mature. You can get started a little bit earlier by starting your nierembergia indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Caribou. In the coldest months of winter you should expect an average low temperature of -30°F.

Since the USDA zone info for Caribou is an average the actual date of last frost changes from year to year. Since half of the time in Caribou you get a frost after May 15 be ready to cover your nierembergia if you have a late frost.

USDA Zone Info for Caribou

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 Caribou

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