The USDA Zone info is a great tool for gardeners to help us determine 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 first chance to plant spearmint in Zone 4b should be figured out by using the USDA zone info.

Planting Calendar for Spearmint

Frost tolerance for spearmint:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Spearmint are very cold tolerant which means that you can start planting them much earlier than plants that are more sensitive to the cold.

The earliest that you can plant spearmint 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 spearmint and expect a good harvest is probably August. You probably don't want to wait any later than that or else your spearmint may not have a chance to grow to maturity. Starting your spearmint indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In Zone 4b the average date of last frost happens on May 15. You should expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for Zone 4b is an average the actual date of last frost can change quite a bit from year to year. Half of the time in Zone 4b you get a frost after May 15 so always be ready to protect your spearmint in the event of a late frost.

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.