Ask Mr. Smarty Plants

First, let me refer you to our article, Container Gardening with Native Plants.  You will see in the article that the recommendation for the size of the pot is: 

"Select a container that will accommodate the full sizes of the plants it will house. It should provide ample root space and have a substantial base to offset top-heaviness (both visually and in terms of stability)."

Winter weather in Wisconsin, however, presents an addtional consideration for the size of the pot you can use.  I believe you can handle the summer heat as long as you pick plants that are happy growing in full sun and you give them adequate water.  However, the winters are another matter.  Roots in a container will not have the same protection from freezing that roots buried in the ground will have.  With container plants you will need to move them to a protected environment to protect their roots as the winter temperatures drop well below freezing.  Consequently, you will need to select plants that fit into containers that you will be able to move to a protected place. You can read advice on preparing container plants for winter weather in the article, Maintaining Winter Gardens in Gladwin, MI, from the National Gardening Association.

Below are shrubs that are Wisconsin natives that grow in full sun.  If the your area is in shade (less than 2 hours sun per day) or part shade (2 to 6 hours of sun per day), you can find recommendations for other plants in our Wisconsin Recommended list.  You can use the NARROW YOUR SEARCH option to limit the list to only 'Shrubs' by choosing that selection under GENERAL APPEARANCE.

Actaea rubra (red baneberry)

Amorpha fruticosa (desert false indigo)

Cornus racemosa (gray dogwood)

Dasiphora fruticosa ssp. floribunda (shrubby cinquefoil)

Physocarpus opulifolius (common ninebark)

Symphoricarpos albus (common snowberry)

Shepherdia canadensis (russet buffaloberry)

Yucca filamentosa (Adam's needle) and here is more information.

Here are photos of the above plants from our Image Gallery:

Actaea rubra

Amorpha fruticosa

Cornus racemosa

Dasiphora fruticosa ssp. floribunda

Physocarpus opulifolius

Symphoricarpos albus

Shepherdia canadensis

Yucca filamentosa