Hi Flowersgalore
Was the problem partly caused by the yarrow being somewhat shaded by surrounding daylily foliage? I think yarrow grows strongest with full sun all the way to the ground.
Yarrow can generally be made less floppy by cutting it back, forcing it to branch low, which helps it be more stable. Such as, when it's 6" high cut it back to 3". Then when it's 12" high cut it back to 6". This is supposing it's one that will grow fairly tall otherwise - say 30".
There are many newer cultivars of yarrow which are much shorter and sturdier but you already know this one will be floppy if not handled differently.
Cutting back will delay the flowering somewhat. If I remember correctly Tracy DiSabato Aust in her book "The Well Tended Perennial Garden" said that a yarrow clump pruned back in 2 steps to different heights produced a longer-blooming clump with flowers at 3 heights. I intend to try it when one of mine is large enough.
I've grown them in pots in ordinary ProMix with fertilizer as seedlings. They grew well, but they weren't kept there til flowering size, just til transplanted. So I don't know if they would have become floppy.
If you grow one very lean it may work or it may just look ratty. It's not a cactus or a succulent.
Pat
