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 reviewed to estimate when it's a good idea to plant trailing portulaca.

Planting Calendar for Trailing Portulaca

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

Since trailing portulaca require warm weather you must wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant trailing portulaca 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 trailing portulaca and expect a good harvest is probably August. You probably don't want to wait any later than that or else your trailing portulaca may not have a chance to really do well. If you are starting your trailing portulaca indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Mercer Island the average date of last frost happens on March 15. It might get as low as 15°F during the coldest months of winter.

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Mercer Island and it can change quite a bit from year to year. Half of the time in Mercer Island you get a frost after March 15 so make sure that you are ready to cover your trailing portulaca in the event of a late frost.

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.