While at Meadowview I coudn't resist finding a tape measure for this thread. The largest ones I could find were the ones growing semi-wild on the property. These pictures were really hard to take as they were in the pond / heavily grassy areas that had plenty of ticks waiting for Phil and I. But here they are!
Just a hair over 5.5"...
And for height we here is one that is roughly 37 1/4".
Its hard to see the plant to it's true scale due to the heavy grass. Here is Phil Sheridan standing next to a -smaller- plant that was runner up for scale growing next to the location but in the water.