One of the problems with using common names (Japanese Silver Grass) for plants is they are often catch-alls for lots of different cultivars. Japanese Silver Grass is a catch-all name for Miscanthus sinensis, and there's a wide variety of them out there in cultivation.

In general, they are hardy to your zone, and most will set viable seed. However, seed from the cultivars which differ most dramatically from the species, like dwarf, variegated and so forth cultivars, are least likely to come true from seed. If you get good ripe seed, and get it to germinate, your chances of getting those unusual characteristics are slim, but you will get plants close to the species.

There are a few named cultivars which are commonly grown from seed, and while they don't necessarily yield exact duplicates of the parent plants, they will grow into nice plants. M.s. 'New Hybrids,' 'Early Hybrids' and 'Late Hybrids' are the most recent additions to this group. Being hybrids, you can never tell just what you'll get from the seed, but they germinate well, and grow into nice plants. M.s. 'Gracillimus' is another variety which is often grown from seed, and has led to many new and exciting cultivars in Miscanthus breeding.

Well I got seed from one that just looked like tall fountain grass w/ large white plumes, and it's nursery tag said Japenese Silver Grass.

The other set I got, I um....seed snatched....(hiding my face) from the local post office, which had these large beautiful Ornamental Grasses that stood about 10ft tall w/ large white plumes, and white 'tiger' striped leaves. When I went to look up info on the Japanese Silver I got from a friends, the pics on the site I looked at, matched the snatched seed parent perfectly.

I'm not looking to get the stripes, just the tall fountain flowing grass, with the large white plumes. I'll sow them this winter and see what happens I guess.