Kim,

Have you tried filling the hollow stem with water and plugging the opening with a small piece of cotton ball? That often adds some stability and time for longer vase life. I realize that if you're using lupines on a large scale, that might not be practical. (I never do more than one or two designs with lupines at once.)

I sometimes have another problem, in which the stems bend in contorted directions to "lean to the light." (I think this is called phototrophism.)