One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's a good idea to determine when it's a good idea to plant achimenes by looking at the USDA zone info for Helena.

Planting Calendar for Achimenes

Frost tolerance for achimenes:	Not tolerant of frost.
When to plant:	After the last frost has passed.

Since achimenes are not cold tolerant it is necessary to wait until after all chance of frost has passed before you can plant them.

The earliest that you can plant achimenes in Helena 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 achimenes and expect a good harvest is probably August. You probably don't want to wait any later than that or else your achimenes may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your achimenes indoors.

Last Frost Date

In Helena the average date of last frost happens on May 15. You can expect an average low temperature of -25°F in the coldest months of winter.

Remember that USDA zone info for Helena is not always accurate and the actual date of last frost is different every year. Since half of the time in Helena there is a last frost after May 15 be ready to protect your achimenes if you have a late frost.

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.