One of the first steps you take when you are making a decision about 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.

In Evanston you can estimate when it's a good idea to plant tree onions by checking out the USDA zone info.

Planting Calendar for Tree onions

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

Since tree onions do ok in moderate cold you can plant them just a tiny bit earlier in the year than more sensitive plants.

The earliest that you can plant tree onions in Evanston 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 tree onions and expect a good harvest is probably August. You probably don't want to wait any later than that or else your tree onions may not have a chance to grow to maturity. If you are starting your tree 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 is on April 15 in Evanston. You can expect an average low temperature of -20°F in the coldest months of winter.

Since the USDA zone info for Evanston is just an average the actual date of last frost changes from year to year. Half of the time in Evanston you get surprised by a frost after April 15 so always be ready to cover your tree onions in the event of one of those late frosts.

USDA Zone Info for Evanston

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 Evanston

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