Ask Mr. Smarty Plants

Ordinarily, when we speak of perennials, we are thinking of herbaceous flowering plants that bloom, set seed, die back to the ground in winter, and re-emerge from the roots in the spring. Your specifications sound more like a blooming bush, which would likely be deciduous, losing its leaves in the fall, but could be of the size you want. We will go to our Recommended Species for Michigan, and search on "shrub" under habit, "part shade" (from 2 to 6 hours of sun a day) under Light Requirements and bloom times of June, July and August. That won't mean the plants we find will bloom all summer, but will bloom at some point during those months. We will list these for you and then you can follow the plant links to the individual pages on each individual plant, learn what size it can be expected to reach, colors, etc. When we ran this search, we got 17 results, and chose 4 that came closest to your specifications. You can repeat the process, using different specifications and make your own choices. Most of these shrubs will benefit from some pruning back in the fall, but some may be better pruned in the spring after they have bloomed. Your USDA Hardiness Zone appears to be Zone 5b (average annual minimum temperature of -20 to -15 deg. F) so any plant recommended for Michigan should be all right in Wayne County in Southeastern Michigan. 

Blooming shrubs for Michigan

Cephalanthus occidentalis (common buttonbush) - evergreen, 6 to 12 ft., blooms white, pink from June to September, high water use, part shade or shade

Diervilla lonicera (northern bush honeysuckle) - deciduous, to 3 ft. tall, blooms red, orange, yellow, purple June to August, low water use, part shade or shade

Hypericum prolificum (shrubby St. Johnswort) - deciduous, to 3 ft. tall, blooms yellow June to August, high water use, part shade or shade

Spiraea alba (white meadowsweet) - deciduous, 3 to 6 ft. tall, blooms white June to September, medium water use, sun, part shade or shade

Cephalanthus occidentalis

Diervilla lonicera

Hypericum prolificum

Spiraea alba