Before planting it is a good idea to find your USDA Zone info to estimate 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.

One way of getting a good idea when it's the best time to plant four-o-clock flower is to use the USDA zone info for Zone 1a.

Planting Calendar for Four-o-clock flower

Frost tolerance for four-o-clock flower:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since four-o-clock flower require warm weather you have to wait until after the last frost has passed before you can plant them.

The earliest that you can plant four-o-clock flower in Zone 1a is June. However, you really should wait until July if you don't want to take any chances.

The last month that you can plant four-o-clock flower and expect a good harvest is probably July. Any later than that and your four-o-clock flower may not have a chance to really do well. You can get started a couple of weeks earlier by starting your four-o-clock flower indoors.

Last Frost Date

On average the last frost has passed is on June 15 in Zone 1a. It might get as low as -60°F during the coldest months of winter.

Since the USDA zone info for Zone 1a is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Zone 1a there is a last frost after June 15 so make sure that you are ready to cover your four-o-clock flower if you have a surprise late frost.

USDA Zone Info for Zone 1a

Here is the info for USDA Zone 1a.

Average Date of Last Frost (spring)	June 15
Average Date of First Frost (fall)	July 15
Lowest Expected Low	-60°F
Highest Expected Low	-55°F

This means that on a really cold year, the coldest it will get is -60°F. On most years you should be prepared to experience lows near -55°F.

Plants to Grow in Zone 1a

You may be interested in your other planting guides for Zone 1a.