One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You will be able to figure out when to plant nigella by using the USDA zone info for Billings.

Planting Calendar for Nigella

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

Nigella do ok in cold weather which tells us that you can plant them earlier in the year than more sensitive plants.

The earliest that you can plant nigella 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 nigella and expect a good harvest is probably August. Any later than that and your nigella may not have a chance to really do well. Starting your nigella indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost is on May 15 in Billings. You should expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for Billings is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Billings you get surprised by a frost after May 15 so just be sure to be ready to cover your nigella in the event of 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.