Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to determine when it's a good idea to plant tree onions by using the USDA zone info for Columbia.

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 are barely cold tolerant you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant tree onions in Columbia 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. If you wait any later than that and your tree onions may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your tree onions indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Columbia. In the coldest months of winter you should expect an average low temperature of -5°F.

Keep in mind that USDA zone info for Columbia is just an average and the actual date of last frost is different every year. Half of the time in Columbia it frosts late in the year after April 15 so be sure to be ready to cover your tree onions in the event of a late frost.

USDA Zone Info for Columbia

Here is the info for USDA Zone 6b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-5°F
Highest Expected Low	0°F

This means that on a really cold year, the coldest it will get is -5°F. On most years you should be prepared to experience lows near 0°F.

Plants to Grow in Columbia

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