One of the first steps you take when you are getting a good idea 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.

You should be able to estimate when to plant campanula by using the USDA zone info for Havre.

Planting Calendar for Campanula

Frost tolerance for campanula:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Since campanula do well in moderate cold you can plant them just a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant campanula in Havre is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant campanula and expect a good harvest is probably August. You probably don't want to wait any later than that or else your campanula may not have a chance to really do well. Starting your campanula indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is May 15 in Havre. In the coldest months of winter you can expect an average low temperature of -30°F.

It's important to remember that USDA zone info for Havre may not be accurate from year to year and the actual date of last frost is different every year. Since half of the time in Havre there is a last frost after May 15 be ready to cover your campanula in the event of one of those late frosts.

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.