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 Sonora should be read to determine when it's possible 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 probably not a good idea to plant periwinkles until after all chance of frost has passed because they require warm weather.

The earliest that you can plant periwinkles in Sonora 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. You probably don't want to wait any later than that or else your periwinkles may not have a chance to really do well. You can get started a little bit earlier by starting your periwinkles indoors.

Last Frost Date

The average date of last frost is February 15 in Sonora. It might get as low as 20°F during the coldest months of winter.

Since the USDA zone info for Sonora may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Since half of the time in Sonora last frost occurs after February 15 be ready to cover your periwinkles if you have a late frost.

USDA Zone Info for Sonora

Here is the info for USDA Zone 9a.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	20°F
Highest Expected Low	25°F

This means that on a really cold year, the coldest it will get is 20°F. On most years you should be prepared to experience lows near 25°F.

Plants to Grow in Sonora

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