The Wister Medal is the highest special medal awarded by the American Iris Society to tall bearded (TB) irises. The candidates are the TBs that have received the Award of Merit 2, 3, or 4 years ago. The winners of the medal are then among those eligible for the American Dykes Medal the following three years.
This year there are 73 candidate TB irises on the 2015 ballot. Below are the first 40 of these (alphabetically). You can see the remaining 33 here.