The USDA Zone info is a great tool for gardeners to help us figure out your gardening 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 Helena should be reffered to in order to figure out when it's possible to plant angelonia.

Planting Calendar for Angelonia

Frost tolerance for angelonia:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since angelonia are barely cold tolerant you can plant them a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant angelonia 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 angelonia and expect a good harvest is probably August. If you wait any later than that and your angelonia may not have a chance to fully mature. You can get started a little bit earlier by starting your angelonia indoors.

Last Frost Date

On average all chance of frost has passed is on May 15 in Helena. You should expect an average low temperature of -25°F in the coldest months of winter.

It's important to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Helena and it is different every year. Half of the time in Helena there is a last frost after May 15 so make sure that you are ready to protect your angelonia in the event of one of those late frosts.

USDA Zone Info for Helena

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Helena

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