Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In Holmen you can figure out when it's possible 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.

Tree onions are one of those plants that can tolerate a tiny bit of cold weather which means that you can start planting them slightly earlier than other plants that might not handle the cold.

The earliest that you can plant tree onions in Holmen is April. However, you really should wait until May 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. If you wait any later than that and your tree onions may not have a chance to fully mature. If you are starting your tree onions indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average all chance of frost has passed is on May 15 in Holmen. In the coldest months of winter you should expect an average low temperature of -25°F.

Just be sure to remember that USDA zone info for Holmen is just an average and the actual date of last frost changes from year to year. Half of the time in Holmen there is a last frost after May 15 so make sure that you are prepared to cover your tree onions if you have one of those late frosts.

USDA Zone Info for Holmen

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Holmen

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