Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A common way of determining when it's a good idea to plant delphinium is to refer to the USDA zone info for Belle Fourche.

Planting Calendar for Delphinium

Frost tolerance for delphinium:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Delphinium are barely cold tolerant which means that you can plant them slightly earlier than plants that are more sensitive to the cold.

The earliest that you can plant delphinium in Belle Fourche 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 delphinium and expect a good harvest is probably August. You probably don't want to wait any later than that or else your delphinium may not have a chance to grow to maturity. You can get started a little bit earlier by starting your delphinium indoors.

Last Frost Date

The average date of last frost is May 15 in Belle Fourche. In the coldest months of winter you can expect an average low temperature of -25°F.

Since the USDA zone info for Belle Fourche is not always accurate the actual date of last frost will vary from year to year. Since half of the time in Belle Fourche there is a last frost after May 15 be ready to protect your delphinium if you have a late frost.

USDA Zone Info for Belle Fourche

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 Belle Fourche

You may be interested in your other planting guides for Belle Fourche.