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 USDA zone info for Zone 4a should be used to figure out when you can plant oenothera.

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 bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant oenothera in Zone 4a 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. Any later than that and your oenothera may not have a chance to really do well. Starting your oenothera indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Zone 4a the average date of last frost happens on May 15. You should expect an average low temperature of -30°F in the coldest months of winter.

Remember that USDA zone info for Zone 4a may not be accurate from year to year and the actual date of last frost will vary from year to year. Since half of the time in Zone 4a it frosts late in the year after May 15 be ready to cover your oenothera in the event of a late frost.

USDA Zone Info for Zone 4a

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°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 -25°F.

Plants to Grow in Zone 4a

You may be interested in your other planting guides for Zone 4a.