The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Snohomish you can figure out when to plant periwinkles by looking at the USDA zone info.

Planting Calendar for Periwinkles

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

Since periwinkles are not cold tolerant you must wait until after the last frost has passed before you can plant them.

The earliest that you can plant periwinkles in Snohomish 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 periwinkles and expect a good harvest is probably August. If you wait any later than that and your periwinkles may not have a chance to fully mature. If you are starting your periwinkles indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Snohomish the average date of last frost happens on March 15. In the coldest months of winter you can expect an average low temperature of 15°F.

Since the USDA zone info for Snohomish is an average the actual date of last frost will vary from year to year. Half of the time in Snohomish you get a frost after March 15 so be sure to be ready to protect your periwinkles if you have a surprise late frost.

USDA Zone Info for Snohomish

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 Snohomish

You may be interested in your other planting guides for Snohomish.