One of the best tools that you have as gardeners to help us determine 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.

You should be able to estimate when to plant tree onions by reviewing the USDA zone info for Idaho Falls.

Planting Calendar for Tree onions

Frost tolerance for tree onions:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since tree onions do ok in moderate cold you can plant them slightly earlier in the year than other plants that might not handle the cold.

The earliest that you can plant tree onions in Idaho Falls 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 tree onions and expect a good harvest is probably August. You probably don't want to wait any later than that or else your tree onions may not have a chance to really do well. Starting your tree onions indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Idaho Falls. You should expect an average low temperature of -20°F in the coldest months of winter.

Since the USDA zone info for Idaho Falls is an average the actual date of last frost is different every year. Half of the time in Idaho Falls there is a last frost after April 15 so make sure that you are prepared to protect your tree onions if you have a surprise late frost.

USDA Zone Info for Idaho Falls

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Idaho Falls

You may be interested in your other planting guides for Idaho Falls.