I like that idea Theo. We use crabapple , Chickasaw plums and honeysuckle and blackberry on wire fences (like long low trellis). We also use small flowering trees like dogwood and redbud for color. Another good large bush is rhododendron (here azalea). I know they will grow in Minn (link) http://www.extension.umn.edu/distribution/horticulture/DG2386.html here is Ill http://www.urbanext.uiuc.edu/shrubselector/detail_plant.cfm?PlantID=422