Blue Flag Iris, Iris versicolor
 
This iris has mesmerizingly beautiful flowers that bloom right in the gap between the spring ephemerals and the summer flowers.
 
Ecology:
Blue flag iris provides early season nectar and pollen to many bee species. Hummingbirds also visit the flowers. It is a host plant to different moth species. Birds love the big seeds. In the wild, the rhizomes help stabilize river slopes and prevent erosion. 
 
Growing conditions:
In the wild, blue flag iris grows in meadows, marshes, swamps and stream banks. It tolerates standing in water but also grows in medium to moist garden soil as long as it doesn't dry out.
 
Water-logged soils are automatically acidic. To create a richer and more acidic soil, leave the leaves and other organic matter to decompose in place. 
 
Good to know:
Iris roots are poisonous.