Bog plants require damp humus-rich soil which does not dry out. However, they will not survive in permanently water-logged soil either.
The best location for bog plants is in a shallow stream, or along the side of the pond where water is allowed to enter the bog area.
There is no clear-cut definition as what is and isn't a bog garden. Many perennials like also flourish in a bog garden too. Follow the garden rules rather than the pond rules for bog plants.
Even though bog plants are planted directly into ground (inside the bog area), they will need to be divided, and taken inside for the winter if they are not hardy to zone four.