Before planting it is a good idea to find your USDA Zone info to figure out 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.

In Ontario you can determine when to plant petunias by referring to the USDA zone info.

Planting Calendar for Petunias

Frost tolerance for petunias:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since petunias do ok in moderate cold you can plant them slightly earlier in the year than more sensitive plants.

The earliest that you can plant petunias 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 petunias and expect a good harvest is probably September. If you wait any later than that and your petunias may not have a chance to really do well. Starting your petunias indoors is a great way to get them started a few weeks earlier.

Last Frost Date

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

Always keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Ontario and it will vary from year to year. Since half of the time in Ontario it frosts late in the year after January 31 be ready to cover your petunias in the event of a 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.