The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By referring to the USDA zone info for Willowbrook you should be able to determine when to 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.

Thunbergia are not cold tolerant which means that you must wait until it warms up after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant thunbergia in Willowbrook 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 thunbergia and expect a good harvest is probably August. If you wait any later than that and your thunbergia may not have a chance to fully mature. If you are starting your thunbergia indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Willowbrook. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Willowbrook is an average the actual date of last frost is different every year. Half of the time in Willowbrook it frosts late in the year after April 15 so just be sure to be ready to protect your thunbergia in the event of a late frost.

USDA Zone Info for Willowbrook

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Willowbrook

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