Before planting it is a good idea to find your USDA Zone info to estimate 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 Portland should be reviewed to figure out when it's the best time to plant periwinkles.

Planting Calendar for Periwinkles

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

Since periwinkles require warm weather it is necessary to wait until after the last frost has passed before you can plant them.

The earliest that you can plant periwinkles in Portland 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 periwinkles and expect a good harvest is probably September. Any later than that and your periwinkles may not have a chance to fully mature. Starting your periwinkles indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In Portland the average date of last frost happens on February 15. You can expect an average low temperature of 25°F in the coldest months of winter.

Remember that USDA zone info for Portland may not be accurate from year to year and the actual date of last frost changes from year to year. Since half of the time in Portland you get a frost after February 15 be ready to protect your periwinkles if you have a late frost.

USDA Zone Info for Portland

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°F

This means that on a really cold year, the coldest it will get is 25°F. On most years you should be prepared to experience lows near 30°F.

Plants to Grow in Portland

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