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

By checking out the USDA zone info for Havre it's a good idea to figure out when it's a good idea to plant thunbergia.

Planting Calendar for Thunbergia

Frost tolerance for thunbergia:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since thunbergia are not cold tolerant you have to wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant thunbergia in Havre 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 thunbergia and expect a good harvest is probably August. You probably don't want to wait any later than that or else your thunbergia may not have a chance to fully mature. You can get started a little bit earlier by starting your thunbergia indoors.

Last Frost Date

The average date of last frost is May 15 in Havre. You can expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Havre may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Havre it frosts late in the year after May 15 be ready to protect your thunbergia if you have a surprise late frost.

USDA Zone Info for Havre

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 Havre

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