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

In Naperville you can figure out when it's the best time to plant onions by referring to the USDA zone info.

Planting Calendar for Onions

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

Since onions are one of those plants that can tolerate quite a bit of cold weather you can plant them earlier in the year than other plants that might not handle the cold.

The earliest that you can plant onions in Naperville 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. You probably don't want to wait any later than that or else your onions may not have a chance to fully mature. If you are starting your onions indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Naperville. It might get as low as -15°F during the coldest months of winter.

Just be sure to remember that USDA zone info for Naperville may not be accurate from year to year and the actual date of last frost will vary from year to year. Half of the time in Naperville there is a last frost after April 15 so make sure that you are prepared to cover your onions in the event of one of those late frosts.

USDA Zone Info for Naperville

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 Naperville

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