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.

The first opportunity to plant oenothera in Ontario should be estimated by referring to the USDA zone info.

Planting Calendar for Oenothera

Frost tolerance for oenothera:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Oenothera do well in some cold which tells us that you can plant them a little bit earlier in the year than more sensitive plants.

The earliest that you can plant oenothera 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 oenothera and expect a good harvest is probably September. Any later than that and your oenothera may not have a chance to really do well. If you are starting your oenothera indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Ontario. In the coldest months of winter you can expect an average low temperature of -15°F.

Just be sure to remember that USDA zone info for Ontario is not always accurate and the actual date of last frost is different every year. Since half of the time in Ontario it frosts late in the year after April 15 be ready to protect your oenothera in the event of a 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.