Keith, most seedlings have just recently come into existence by crosses a
hybridizer has made. Seedlings are then grown for a number of
years so the hybridizer can evaluate it to see if they have all
it takes to be introduced to the public. This usually includes
branching, growth habits and overall health of the plant, form and substance of
the iris flower itself, bud placement, etc., Only time will tell - if any
of these "seedlings" will ever be for sale.
Many of us like to see (either in person or in photos) the up and coming
"seedlings" to get an idea of what is on the horizon.
I hope this helps to clarify things a little for you.