One of the best tools that you have as gardeners to help us figure out your gardening schedule is the 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.

It's a good idea to figure out when you can plant oenothera by using the USDA zone info for Ottawa.

Planting Calendar for Oenothera

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

Since oenothera are one of those plants that can tolerate a little bit of cold weather you can plant them a little earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant oenothera in Ottawa 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. If you wait any later than that and your oenothera may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your oenothera indoors.

Last Frost Date

The average date of last frost is April 15 in Ottawa. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Ottawa is an average the actual date of last frost is different every year. Half of the time in Ottawa you get a frost after April 15 so make sure that you are ready to protect your oenothera in the event of a surprise late frost.

USDA Zone Info for Ottawa

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 Ottawa

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