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.

You should be able to figure out when it's a good idea to plant onions by checking out the USDA zone info for Columbus.

Planting Calendar for Onions

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

Onions do ok in a bit of cold which tells us that you can plant them much earlier in the year than other plants that might not handle the cold.

The earliest that you can plant onions in Columbus is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant onions and expect a good harvest is probably September. Any later than that and your onions may not have a chance to grow to maturity. If you are starting your onions indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Columbus. It might get as low as -10°F during the coldest months of winter.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Columbus and it is different every year. Since half of the time in Columbus last frost occurs after April 15 be ready to cover your onions in the event of one of those late frosts.

USDA Zone Info for Columbus

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Columbus

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