I'd keep it. :) I planted my maudry last year and was worried it might not make it through the winter (some places list it as a zone 5/6) but it's greening up nicely. As far as it being invasive, I'm not too worried about it. In some states it is but I've also read where people have had it for a few years without seeing any seedlings.

Ouch! I just picked up a Moudry fountain grass at a plant swap last weekend. Didn't realize it was so invasive. I might look for something else rather than deal with it, as the plant didn't cost me anything. Here in NC, invasive plants can really be a hassle due to all the rain we get. I'm just realizing how invasive N. Sea Oats can be. I planted a couple last year and they were one of my favorite grasses. However, now I've got little sea oats seedlings coming up everywhere within about 8-10' of the parents.

Moudry is a vigorous self seeder. If you cut the flower heads off before they dry on the plant, they do not then have a chance to self sow. They bloom very late in the season for us here. In colder zones such as yours I don't know if there would be time for the seedheads to mature to the point of self sowing.
Jack

Jack, just how late does it bloom in zone 7? I'm still wondering if I wasted my money...bought 3 of these. I wanted to enjoy looking at the flowers before a hard frost hit.....hmmmm.

Well here's my 2 cents. I have been growing 'Moudry' for nearly 7 years in the Seattle, Washington area, z8. I have grown her in many different gardens, locations and planting styles - like mass planting and specimen. Depending on all of the varying conditions of sun, water, food, competition, length and average temp. of the seasons and so on she may or may not flower here, although usually does when really happy. I have grow literally hundreds and maybe thousands of clumps of this grass and have very, very rarely gotten any seedling re-sowing. All of these were grown in fertile enviroments with regular water and always were left to seed, not being cut down until mid-march. I am sure there are areas were 'Moudry' does re-seed, but not for me, and not here. Around here the re-seeders are blue fescue, leatherleaf sedge, and blue oat grass. And all of these are more commen around the Northwest than 'Moudry'. This - Black Flowering Fountain Grass is one of my most favorite Ornamental Grasses, and I grow almost a hundered kinds of grasses and grass likes. It is such a lush green, wide bladed fountain when grown right and the purple/bleck seedheads are really nice. Rick Darke's Book gives here a bad rap and alot of people miss out on this beauty out of fear of being grown out of their yards with grass (this ain't bamboo or forget me not's). I must say though that I am certain that in some places any plant given the right condition can become invasive or an epidemic.

Gardenlady-
Blooms here usually late Sept., sometimes weather conditions cause earlier flowering.
Jack