One of the best tools that you have as gardeners to help us figure out 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 estimate when it's a good idea to plant bunching onions by referring to the USDA zone info for Caribou.

Planting Calendar for Bunching Onions

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

Since bunching onions do ok in moderate cold you can plant them just a tiny bit earlier in the year than more sensitive plants.

The earliest that you can plant bunching onions in Caribou is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant bunching onions and expect a good harvest is probably August. You probably don't want to wait any later than that or else your bunching onions may not have a chance to grow to maturity. If you are starting your bunching onions indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Caribou the average date of last frost happens on May 15. You should expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Caribou is an average the actual date of last frost will vary from year to year. Half of the time in Caribou it frosts late in the year after May 15 so just be sure to be ready to cover your bunching onions if you have one of those late frosts.

USDA Zone Info for Caribou

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Caribou

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