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.

By referring to the USDA zone info for Ontario it's possible to figure out when it's the best time to plant corn.

Planting Calendar for Corn

Frost tolerance for corn:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since corn require warm weather you must wait until after the last frost has passed before you can plant them.

The earliest that you can plant corn in Ontario is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant corn and expect a good harvest is probably August. You probably don't want to wait any later than that or else your corn may not have a chance to fully mature. Starting your corn indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Ontario. You should expect an average low temperature of -15°F in the coldest months of winter.

Since the USDA zone info for Ontario is just an average the actual date of last frost is different every year. Half of the time in Ontario it frosts late in the year after April 15 so be sure to be ready to cover your corn if you have a surprise late frost.

USDA Zone Info for Ontario

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Ontario

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