Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to figure out when it's possible to plant oenothera by looking at the USDA zone info for Billings.

Planting Calendar for Oenothera

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

Oenothera can survive in a little bit of cold which means that you can plant them a little bit earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant oenothera and expect a good harvest is probably August. If you wait any later than that and your oenothera may not have a chance to grow to maturity. If you are starting your oenothera indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Billings the average date of last frost happens on May 15. In the coldest months of winter you should expect an average low temperature of -25°F.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Billings and it changes from year to year. Half of the time in Billings you get surprised by a frost after May 15 so make sure that you are ready to protect your oenothera if you have a late frost.

USDA Zone Info for Billings

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Billings

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