Pickerel Rush (Pontederia cordata) has heart shaped foliage that is shiny and a dark green color.  One of the favorites of pond owners.  Easy to grow and hardy Zones 5-11.  It grows in sun to part shade in moist soil or water up to 10 inches deep.  So for the colder states this is truly a good plant for your water garden.  It has large spikes of purple flowers that appear throughout the summer and requires little maintenance.  It will grow to about 2 feet high and about 2 feet wide.

Available Purple Pickerel Rush here.