One of the first steps you take when you are determining 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.

In Helena you can determine when it's a good idea to plant four-o-clock flower by using the USDA zone info.

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.

It's not a good idea to plant four-o-clock flower until after the last frost because they require warm weather.

The earliest that you can plant four-o-clock flower in Helena is April. However, you really should wait until May 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 August. You probably don't want to wait any later than that or else your four-o-clock flower may not have a chance to fully mature. If you are starting your four-o-clock flower indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is March 15 in Helena. You can expect an average low temperature of 10°F in the coldest months of winter.

Since the USDA zone info for Helena is not always accurate the actual date of last frost can change quite a bit from year to year. Since half of the time in Helena it frosts late in the year after March 15 be ready to protect your four-o-clock flower if you have one of those late frosts.

USDA Zone Info for Helena

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Helena

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