Successfully Grow Mums
I had great success growing mums at my old house. In my new home both the old mums I brought with me and new ones I have purchased at the store have died. Both are in zone 5 and the only differences I can see is the old planting location was between a basement wall and concrete sidewalk with no mulch and the new location is between an unheated garage wall and service walk with stone mulch.
The original planting location may have been a bit more sheltered than the new site. Plus hardy mums are not always reliably hardy in colder climate. Try Mammoth Mum™ or one of the other zone 3 hardy mums developed by the University of Minnesota. This prolific bloomer has thrived at the Green Bay Botanical Gardens for several years. In the meantime increase your success through proper planting and care. A well tended plant is less likely to die over winter. You may want to replace the stone mulch with organic mulch such as shredded leaves, evergreen needles or twice-shredded bark. Remove any weed barrier so as the organic mulch breaks down it improves the soil. Try planting new mums in spring to allow the plants to become established before blooming and the often harsh winters. Amend the soil by adding organic matter to the soil whenever planting or transplanting mums. These fall bloomers prefer moist well drained soils and tend to survive winters better under these conditions. Allow the plants to stand over winter, cutting them back in late winter or early spring. Research has shown this practice increases winter hardiness. Add a bit of extra protection by mulching the plants with straw or evergreen boughs after the ground freezes.