Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first chance to plant periwinkles in Portola Valley should be estimated by referring to the USDA zone info.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since periwinkles require warm weather you have to wait until after the last frost before you can plant them.

The earliest that you can plant periwinkles in Portola Valley 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 periwinkles and expect a good harvest is probably September. Any later than that and your periwinkles may not have a chance to grow to maturity. Starting your periwinkles indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost is on January 31 in Portola Valley. You should expect an average low temperature of 30°F in the coldest months of winter.

Since the USDA zone info for Portola Valley may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Portola Valley you get a frost after January 31 be ready to cover your periwinkles in the event of one of those late frosts.

USDA Zone Info for Portola Valley

Here is the info for USDA Zone 10a.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	30°F
Highest Expected Low	35°F

This means that on a really cold year, the coldest it will get is 30°F. On most years you should be prepared to experience lows near 35°F.

Plants to Grow in Portola Valley

You may be interested in your other planting guides for Portola Valley.