Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. 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 looked at to estimate when it's possible to plant bougainvillea.

Planting Calendar for Bougainvillea

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

Since bougainvillea require warm weather you must wait until after the last frost has passed before you can plant them.

The earliest that you can plant bougainvillea 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 bougainvillea and expect a good harvest is probably August. If you wait any later than that and your bougainvillea may not have a chance to really do well. You can get started a couple of weeks earlier by starting your bougainvillea indoors.

Last Frost Date

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

Keep in mind that USDA zone info for Mercer Island is not always accurate and the actual date of last frost will vary from year to year. Half of the time in Mercer Island last frost occurs after March 15 so make sure that you are prepared to cover your bougainvillea 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.