One of the first steps you take when you are getting a good idea 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 Mercer Island should be reviewed 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 has passed.

It's a bad idea to plant thunbergia until after all chance of frost has passed because they are not cold tolerant.

The earliest that you can plant thunbergia in Mercer Island 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 really do well. You can get started a little bit earlier by starting your thunbergia indoors.

Last Frost Date

In Mercer Island the average date of last frost happens on March 15. You should expect an average low temperature of 15°F in the coldest months of winter.

Remember that USDA zone info for Mercer Island 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 Mercer Island last frost occurs after March 15 be ready to cover your thunbergia if you have one of those late frosts.

USDA Zone Info for Mercer Island

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°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 20°F.

Plants to Grow in Mercer Island

You may be interested in your other planting guides for Mercer Island.