Black flowered is the description, the name is "iris chrysographes". The small letters indicate it is a species so originally from the wild and it belongs to the siberian class. Here are some pictures and history of it.
http://wiki.irises.org/bin/rdi... The White Flower Farms page you showed us has some culture info in the right hand column.
Also there is a Siberian Iris Society and here are culture notes
http://www.socsib.org/ssicult....
I'm not growing any lately, but have and soaking before planting is a very good idea. You never want to let a Siberian get completely dry. Obviously you will not get flowers this year. Sometimes it will be two years after planting before you have bloom. They are not fond of being moved, but they can be transplanted both spring and fall. In the spring before flowering I always gave my plants at least a couple of deep waterings as they started to grow taller and develop stalks and buds.
Before planting let them soak one to two days at most. If still not able to plant you could pot in pure peat for a few days. just keep it moist.
Good luck.
