Is best in full sun so a free-standing location away from any fence or wall is best. And NO fertilizer (even in close but not direct proximity).

I live less than a block from the beach in an area prone to some strong winds and KF holds up well, even in rain.

FWIW, too rich a soil, too much water, any type of fertilization and a poor siting can encourage floppiness.

Thanks so much! It may be time to say goodbye to it then. I like it as a filler, but I much prefer my flowering perennials.

The fence location is more the problem than nearby fertilizer. If you have a full sun location out in the open it is worth transplanting.

Different zone (7) but we had trouble with Karl Forrester long ago. I wanted it to work and saw it as the most “architectural” of ornamental grasses for a large grid of grass-only-single-species garden for a rigid look in neat rows. It didn‘t work out. With advice from a landscape architect we replaced all with a native panicum grass called Heavy Metal (but there are several panicums native to the US prairies). It worked out very well with little care.

You aren't crazy, or at least not alone: I'm in 5a and had similar troubles with the Foerster. Full sun, but situated next to my front steps among perennials that I did fertilize, so perhaps that was my issue. Replaced it with Dewey Blue which was even worse (and bigger, so even more flops) and last year threw in Northern Sea Oats, which are behaving quite well, no flopping, and have really fabulous little seedheads all winter.

yep mine flops (we are in uk). Its disappointing given it's 'strong architectural', 'wind proof' decription. We are shaded part of the day as on side of a hill. So I don't think we get enough sun. I planted it along a path and every time it rains, it falls across path and you either brace yourself for a bath as the flowers and foliage deposit all their water on you or go the long way round. Ive had to prop it up with a makeshift bamboo fence. This summer we had non-stop sun and it was the best 'upright' year ever! I'm wary now of planting in clients' garden now unless they are south facing and full sun.