One of the first steps you take when you are determining 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.

The USDA zone info for Ironwood can be read to figure out when you can plant thunbergia.

Planting Calendar for Thunbergia

Frost tolerance for thunbergia:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

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

The earliest that you can plant thunbergia in Ironwood 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. Any later than that and your thunbergia may not have a chance to fully mature. You can get started a few weeks earlier by starting your thunbergia indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Ironwood. You can expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Ironwood is just an average the actual date of last frost changes from year to year. Half of the time in Ironwood you get a frost after May 15 so make sure that you are ready to cover your thunbergia if you have one of those late frosts.

USDA Zone Info for Ironwood

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 Ironwood

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