One of the best tools that you have as gardeners to help us figure out your gardening schedule is the 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.

A common way of getting a good idea when to plant dahlias is to use the USDA zone info for Holmen.

Planting Calendar for Dahlias

Frost tolerance for dahlias:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

You should not plant dahlias until after the last frost because they do not do well in cold weather.

The earliest that you can plant dahlias in Holmen is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant dahlias and expect a good harvest is probably August. Any later than that and your dahlias may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your dahlias indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Holmen. It might get as low as -25°F during the coldest months of winter.

Remember that USDA zone info for Holmen is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Holmen it frosts late in the year after May 15 so always be ready to cover your dahlias 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.