The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The earliest that you can plant periwinkles in Spearfish should be determined by checking out the USDA zone info.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After the last frost has passed.

It's a bad idea to plant periwinkles until after the last frost when the weather gets warmer because they do not do well in cold weather.

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

The last month that you can plant periwinkles and expect a good harvest is probably August. Any later than that and your periwinkles may not have a chance to really do well. You can get started a couple of weeks earlier by starting your periwinkles indoors.

Last Frost Date

In Spearfish the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of -20°F.

Remember that USDA zone info for Spearfish is an average and the actual date of last frost is different every year. Since half of the time in Spearfish you get a frost after April 15 be ready to protect your periwinkles in the event of a late frost.

USDA Zone Info for Spearfish

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 Spearfish

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