One of the best tools that you have as gardeners to help us figure out your gardening schedule is the 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 used to determine when you can plant purple coneflower.

Planting Calendar for Purple Coneflower

Frost tolerance for purple coneflower:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

You can plant purple coneflower just a tiny bit earlier in the year because they do ok in moderate cold.

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

The last month that you can plant purple coneflower and expect a good harvest is probably August. Any later than that and your purple coneflower may not have a chance to fully mature. Starting your purple coneflower indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is March 15 in Mercer Island. In the coldest months of winter you should expect an average low temperature of 15°F.

It's important to remember that USDA zone info for Mercer Island may not be accurate from year to year and the actual date of last frost changes from year to year. Half of the time in Mercer Island it frosts late in the year after March 15 so just be sure to be ready to protect your purple coneflower in the event of 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.