One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By looking at the USDA zone info for Waterloo it's possible to figure out when you can plant tree onions.

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.

Tree onions do well in some cold which means that you can plant them just a tiny bit earlier in the year than other frost tender plants.

The earliest that you can plant tree onions in Waterloo 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. Starting your tree onions indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In Waterloo the average date of last frost happens on April 15. In the coldest months of winter you should expect an average low temperature of -20°F.

It's important to remember that the actual date of last frost is an average because it is based on the USDA zone info for Waterloo and it can change quite a bit from year to year. Since half of the time in Waterloo there is a last frost after April 15 be ready to protect your tree onions in the event of one of those late frosts.

USDA Zone Info for Waterloo

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 Waterloo

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