One of the first steps you take when you are figuring out your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Oak Brook should be looked at to determine when it's the best time to plant bunching onions.

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.

You can plant bunching onions slightly earlier in the year because they are barely cold tolerant.

The earliest that you can plant bunching onions in Oak Brook 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 bunching onions and expect a good harvest is probably August. Any later than that and your bunching onions may not have a chance to fully mature. You can get started a little bit earlier by starting your bunching onions indoors.

Last Frost Date

In Oak Brook the average date of last frost happens on April 15. It might get as low as -15°F during the coldest months of winter.

Always keep in mind that USDA zone info for Oak Brook 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 Oak Brook there is a last frost after April 15 so make sure that you are prepared to protect your bunching onions if you have one of those late frosts.

USDA Zone Info for Oak Brook

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 Oak Brook

You may be interested in your other planting guides for Oak Brook.