The USDA Zone info is a great tool for gardeners to help us figure out 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.

A common way of determining when it's possible to plant welsh onion is to use the USDA zone info for Prospect Heights.

Planting Calendar for Welsh onion

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

You can plant welsh onion slightly earlier in the year because they are barely cold tolerant.

The earliest that you can plant welsh onion in Prospect Heights 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 welsh onion and expect a good harvest is probably August. You probably don't want to wait any later than that or else your welsh onion may not have a chance to grow to maturity. Starting your welsh onion indoors is a great way to get them started a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Prospect Heights. It might get as low as -15°F during the coldest months of winter.

It's important to remember that USDA zone info for Prospect Heights is not always accurate and the actual date of last frost changes from year to year. Half of the time in Prospect Heights it frosts late in the year after April 15 so always be ready to cover your welsh onion in the event of a surprise late frost.

USDA Zone Info for Prospect Heights

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 Prospect Heights

You may be interested in your other planting guides for Prospect Heights.