'Karl Foerster' is a hybrid and like a number of hybrid plants does not produce fertile seeds. The seed sterility is one of this grass's pluses if you ask me - it will never self-sow and become a pest like many other OG's can do in ideal situations (I am now avoiding all species of Stipa or their relatives for this reason). If you do find online sources for the seeds, they are not true to name and I'd advise against purchasing them. 'Karl Foerster' is propagated by divisions only, as are the variegated forms of feather reed grass as well.