The University of Minnesota has developed many many hardy plants for our zone 4 climate. Thanks to the U of MN, we have great apples such as 'HoneyCrisp' and a series of Azaleas called 'Northern Lights'. One interesting plant that not many people know about is: Exochorda serratifolia,
common name: Pearlbush 'Northern Pearls'.
This variety was released in 1995. At first glance, you'd think it's a mockorange, but there's no fragrance, and the Pearlbush has PEARLS! The flower buds look like a string of pearls. The flower shape is strange too- not the same as Mockorange.
The woody shrub grows to 8-10 feet tall. The flowering is on the top, like a mockorange or lilac. The best time to see it is right now, when you have bud and bloom at the same time.