One of the first steps you take when you are figuring out your gardening schedule is find your 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.

The first opportunity to plant four o' clock in Zone 4a should be determined by referring to the USDA zone info.

Planting Calendar for Four O' Clock

Frost tolerance for four o' clock:	Not tolerant of frost.
When to plant:	After the last frost.

Four O' Clock are not cold tolerant which means that it's important to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant four o' clock in Zone 4a is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant four o' clock and expect a good harvest is probably August. Any later than that and your four o' clock may not have a chance to really do well. Starting your four o' clock indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost has passed is on May 15 in Zone 4a. In the coldest months of winter you can expect an average low temperature of -30°F.

Since the USDA zone info for Zone 4a is an average the actual date of last frost changes from year to year. Since half of the time in Zone 4a there is a last frost after May 15 be ready to protect your four o' clock if you have 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.