One of the best tools that you have as gardeners to help us determine your gardening schedule is the 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 reffered to in order to determine when it's the best time to plant diascia.

Planting Calendar for Diascia

Frost tolerance for diascia:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

You can plant diascia a little earlier in the year because they are moderately cold tolerant.

The earliest that you can plant diascia in Mercer Island is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant diascia and expect a good harvest is probably September. You probably don't want to wait any later than that or else your diascia may not have a chance to fully mature. If you are starting your diascia indoors then you might be able to get away with starting them a little bit earlier.

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.

Since the USDA zone info for Mercer Island is just an average the actual date of last frost will vary from year to year. Since half of the time in Mercer Island you get a frost after March 15 be ready to cover your diascia if you have 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.