One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By referring to the USDA zone info for Zone 4b you should be able to figure out when it's the best time to plant campanula.

Planting Calendar for Campanula

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

You can plant campanula just a bit earlier in the year because they are one of those plants that can tolerate a little bit of cold weather.

The earliest that you can plant campanula in Zone 4b 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. If you wait any later than that and your campanula may not have a chance to really do well. You can get started a little bit earlier by starting your campanula indoors.

Last Frost Date

The average date of last frost is May 15 in Zone 4b. It might get as low as -25°F during the coldest months of winter.

Since the USDA zone info for Zone 4b may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Zone 4b it frosts late in the year after May 15 so be sure to be ready to cover your campanula if you have one of those late frosts.

USDA Zone Info for Zone 4b

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 Zone 4b

You may be interested in your other planting guides for Zone 4b.