One of the first steps you take when you are estimating your gardening schedule is find your 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 getting a good idea when to plant verbena is to look at the USDA zone info for Caribou.

Planting Calendar for Verbena

Frost tolerance for verbena:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Verbena tend to make it in some cold which means that you can plant them a bit earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant verbena and expect a good harvest is probably August. If you wait any later than that and your verbena may not have a chance to really do well. You can get started a little bit earlier by starting your verbena indoors.

Last Frost Date

In Caribou the average date of last frost happens on May 15. You can expect an average low temperature of -30°F in the coldest months of winter.

Keep in mind that USDA zone info for Caribou is not always accurate and the actual date of last frost can change quite a bit from year to year. Since half of the time in Caribou there is a last frost after May 15 be ready to protect your verbena in the event of a surprise 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.