One of the first steps you take when you are figuring out your gardening schedule is find your 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.

A way of figuring out when it's a good idea to plant spearmint is to consult the USDA zone info for Casper.

Planting Calendar for Spearmint

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

Spearmint tend to make it in pretty solid cold which tells us that you can plant them a lot earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant spearmint and expect a good harvest is probably September. You probably don't want to wait any later than that or else your spearmint may not have a chance to grow to maturity. If you are starting your spearmint indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average the last frost is on April 15 in Casper. In the coldest months of winter you should expect an average low temperature of -20°F.

Since the USDA zone info for Casper is not always accurate the actual date of last frost will vary from year to year. Half of the time in Casper it frosts late in the year after April 15 so always be ready to cover your spearmint if you have one of those late frosts.

USDA Zone Info for Casper

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Casper

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