One of the first steps you take when you are figuring out your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By looking at the USDA zone info for Billings you will be able to estimate when to plant rosemary.

Planting Calendar for Rosemary

Frost tolerance for rosemary:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

You can plant rosemary quite a bit earlier in the year because they are one of those plants that can tolerate quite a bit of cold weather.

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

Last Frost Date

In Billings the average date of last frost happens on May 15. It might get as low as -25°F during the coldest months of winter.

Keep in mind that USDA zone info for Billings may not be accurate from year to year and the actual date of last frost will vary from year to year. Half of the time in Billings last frost occurs after May 15 so always be ready to cover your rosemary if you have one of those late frosts.

USDA Zone Info for Billings

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 Billings

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