The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

By using the USDA zone info for Bloomington you should be able to determine when it's the best time to plant tree onions.

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 frost tender plants.

The earliest that you can plant tree onions in Bloomington 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 fully mature. You can get started a couple of weeks earlier by starting your tree onions indoors.

Last Frost Date

In Bloomington the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that USDA zone info for Bloomington is just an average and the actual date of last frost changes from year to year. Since half of the time in Bloomington you get a frost after April 15 be ready to cover your tree onions if you have a surprise late frost.

USDA Zone Info for Bloomington

Here is the info for USDA Zone 5b.

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

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Bloomington

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