Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In Polson you can determine when it's possible to plant nigella by looking at the USDA zone info.

Planting Calendar for Nigella

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

Nigella tend to make it in pretty solid cold which means that you can plant them a lot earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant nigella in Polson is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant nigella and expect a good harvest is probably September. If you wait any later than that and your nigella may not have a chance to grow to maturity. If you are starting your nigella indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Polson the average date of last frost happens on April 15. It might get as low as -10°F during the coldest months of winter.

Since the USDA zone info for Polson is just an average the actual date of last frost changes from year to year. Since half of the time in Polson you get a frost after April 15 be ready to cover your nigella in the event of a late frost.

USDA Zone Info for Polson

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Polson

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