Potentilla fruticosa [Bush Cinquefoil]
Extreme hardiness and long season of bloom make this a favorite in severe climates. Low stature and tolerance of poor, dry soils give it added usefulness in other areas also. Can develop a ragged, unkept habit over time. Remove 1/3 of canes each year (3-year pruning cycle), and consider renewal pruning to a very low framework every 3-5 years if needed.