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.

It's a good idea to estimate when to plant thunbergia by looking at the USDA zone info for Great Falls.

Planting Calendar for Thunbergia

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

Thunbergia do not do well in cold weather which tells us that it's important to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant thunbergia in Great Falls 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 grow to maturity. Starting your thunbergia indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Great Falls the average date of last frost happens on May 15. It might get as low as -30°F during the coldest months of winter.

Keep in mind that USDA zone info for Great Falls is an average and the actual date of last frost can change quite a bit from year to year. Since half of the time in Great Falls you get a frost after May 15 be ready to protect your thunbergia in the event of a surprise late frost.

USDA Zone Info for Great Falls

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 Great Falls

You may be interested in your other planting guides for Great Falls.