The USDA Zone info is a great tool for gardeners to help us determine your gardening 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 San Rafael can be reffered to in order to estimate 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 has passed.

It's a bad idea to plant periwinkles until after all chance of frost has passed because they are not cold tolerant.

The earliest that you can plant periwinkles in San Rafael 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. 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 San Rafael the average date of last frost happens on January 31. It might get as low as 30°F during the coldest months of winter.

Since the USDA zone info for San Rafael is an average the actual date of last frost changes from year to year. Since half of the time in San Rafael you get surprised by a frost after January 31 be ready to cover your periwinkles if you have one of those late frosts.

USDA Zone Info for San Rafael

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 San Rafael

You may be interested in your other planting guides for San Rafael.