One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. 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 you can plant iberis is to consult the USDA zone info for Havre.

Planting Calendar for Iberis

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

Iberis do well in moderate cold which tells us that you can get them planted earlier than other frost tender plants.

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

Last Frost Date

On average the last frost has passed is on May 15 in Havre. You should expect an average low temperature of -30°F in the coldest months of winter.

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Havre and it can change quite a bit from year to year. Half of the time in Havre it frosts late in the year after May 15 so always be ready to protect your iberis in the event of a late frost.

USDA Zone Info for Havre

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 Havre

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