One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Ontario should be reffered to in order to determine when it's a good idea to plant periwinkles.

Planting Calendar for Periwinkles

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

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

The earliest that you can plant periwinkles in Ontario 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. If you wait any later than that and your periwinkles may not have a chance to really do well. Starting your periwinkles indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Ontario the average date of last frost happens on January 31. You should expect an average low temperature of 30°F in the coldest months of winter.

Since the USDA zone info for Ontario is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Ontario you get surprised by a frost after January 31 so just be sure to be ready to cover your periwinkles if you have a surprise late frost.

USDA Zone Info for Ontario

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 Ontario

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