It depends, but most will not spread by seeds. A few can. You are really vague here, and are you saying that the name "Tiger Grass" is your made up name?

Yes, I am vague. I have no idea which grass is which, so that's why I joined this forum. To learn from the pro's.

Tiger Grass -- Yes that is what I call it. The leaves are deep green with 1/4 to 1/2" white stripes about every 6" or so. Any idea on the real name?

Most likely a form of Miscanthus sinensis, silver or maiden grass. There are numerous cultivars with horizontal banding - 'Strictus', 'Zebrinus', 'Little Nicky', 'Goldbar', etc. They are often commonly referred to as zebra or porcupine grass but tiger grass works just as well and certainly indicates its striped nature :-) And none of these are likely to set viable seed, so little concern of excessive spreading (although the clumps will definitely increase in size as time passes).

Did the nursery not have these plants clearly labeled with the correct botanical name? Seems like a very careless oversight if not.