The USDA Zone info is a great tool for gardeners to help us figure out 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 best time to plant helianthemum in Iron Mountain should be determined by looking at the USDA zone info.

Planting Calendar for Helianthemum

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

Helianthemum are one of those plants that can tolerate a little bit of cold weather which tells us that you can plant them a little bit earlier than other frost tender plants.

The earliest that you can plant helianthemum in Iron Mountain 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 really do well. You can get started a few weeks earlier by starting your helianthemum indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Iron Mountain. You should expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Iron Mountain is just an average the actual date of last frost is different every year. Half of the time in Iron Mountain last frost occurs after May 15 so make sure that you are prepared to protect your helianthemum if you have a late frost.

USDA Zone Info for Iron Mountain

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Iron Mountain

You may be interested in your other planting guides for Iron Mountain.