Did you read my
tiger lilly page?
There are a lot of flowers known as tigerlillies. If we are talking about the same plant, They should have spread fine. tiger lillies have bulbils between the leaf and stem. all the bulbils come up...it takes awhile for them to do anything though.
Has the soil been worked? This would be the no 1 reason for most stuff to not do well. Then there is voles which eat the bulbs out from under the plant...you go out and see the stem sticking out of a hole in the ground...
How many hours of sun do your tiger lillies get?