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

You should be able to determine when you can plant helianthemum by looking at the USDA zone info for Belle Fourche.

Planting Calendar for Helianthemum

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

Since helianthemum do well in moderate cold you can plant them just a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant helianthemum in Belle Fourche 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 helianthemum and expect a good harvest is probably August. If you wait any later than that and your helianthemum may not have a chance to fully mature. Starting your helianthemum indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Belle Fourche. You can expect an average low temperature of -25°F in the coldest months of winter.

It's important to remember that the actual date of last frost is an average because it is based on the USDA zone info for Belle Fourche and it will vary from year to year. Since half of the time in Belle Fourche last frost occurs after May 15 be ready to cover your helianthemum in the event of a surprise 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.