The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to determine when to plant onions by checking out the USDA zone info for Charles City.

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 means 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 Charles City 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. If you wait any later than that and your onions may not have a chance to grow to maturity. Starting your onions indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Charles City. In the coldest months of winter you can expect an average low temperature of -20°F.

Since the USDA zone info for Charles City may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Charles City you get a frost after April 15 so always be ready to cover your onions in the event of one of those late frosts.

USDA Zone Info for Charles City

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 Charles City

You may be interested in your other planting guides for Charles City.