One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

By reviewing the USDA zone info for Helena you will be able to estimate when you can plant pentas.

Planting Calendar for Pentas

Frost tolerance for pentas:	Not tolerant of frost.
When to plant:	After the last frost.

Since pentas require warm weather you have to wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant pentas 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 pentas and expect a good harvest is probably August. If you wait any later than that and your pentas may not have a chance to really do well. Starting your pentas indoors is a great way to get them started 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 is different every year. Since half of the time in Helena it frosts late in the year after March 15 be ready to protect your pentas if you have a late frost.

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.