Keep pulling them, and don't let any of them flower or go to seed.

You should dig some up and send them to me, lol.

They pull out of the ground very easily. Pull every time you see one where you don't want it to grow.

In the future, you can restrain seeding somewhat by "combing" the grass clump when it starts to set seed. Be certain you have a large container nearby to stash the "combings."

Thanks all. Jungle87, I have a better idea, why don't you come pull them and take all you want?

Actually I've pulled most of the larger weeds, removed the top 1/2 to inch of soil (with the hope of removing more of the dratted feather grass seeds) and will now lay down landscape cloth (easier to get in quantity than newspaper - although I would prefer newspaper because it breaks down and adds something to the soil) and then lay 3-4 inches of shredded hemlock bark on top. That, I hope, will do the trick. Cheers!

I've grown it for over ten years and have multiple clumps and never had such a problem with it seeding. I actually let them grow and pot them up and sell them. They ship easily when small.