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.

It's a good idea to determine when you can plant onions by referring to the USDA zone info for Bozeman.

Planting Calendar for Onions

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

Since onions do well in cold you can plant them earlier in the year than plants that are more sensitive to the cold.

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

Last Frost Date

On average all chance of frost has passed is on May 15 in Bozeman. It might get as low as -25°F during the coldest months of winter.

Remember that the actual date of last frost is an average because it is based on the USDA zone info for Bozeman and it changes from year to year. Half of the time in Bozeman you get a frost after May 15 so make sure that you are prepared to protect your onions in the event of a surprise late frost.

USDA Zone Info for Bozeman

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 Bozeman

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