One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Mercer Island can be looked at to figure out when it's a good idea to plant zinnia.

Planting Calendar for Zinnia

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

Zinnia are not cold tolerant which tells us that you must wait until it warms up after the last frost before you can plant them.

The earliest that you can plant zinnia 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 zinnia and expect a good harvest is probably August. Any later than that and your zinnia may not have a chance to grow to maturity. If you are starting your zinnia indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is 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 an average and the actual date of last frost is different every year. Half of the time in Mercer Island you get a frost after March 15 so always be ready to cover your zinnia 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.