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

The first opportunity to plant calliopsis in Havre should be figured out by referring to the USDA zone info.

Planting Calendar for Calliopsis

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

Calliopsis require warm weather which tells us that it's important to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant calliopsis in Havre 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 calliopsis and expect a good harvest is probably August. Any later than that and your calliopsis may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your calliopsis indoors.

Last Frost Date

On average all chance of frost has passed is on May 15 in Havre. In the coldest months of winter you can expect an average low temperature of -30°F.

Since the USDA zone info for Havre may not be accurate from year to year the actual date of last frost is different every year. Since half of the time in Havre you get surprised by a frost after May 15 be ready to protect your calliopsis if you have a surprise late frost.

USDA Zone Info for Havre

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Havre

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