Betty,
My rhizomes are rather small too. I never feed mine, I know, I know, but there is only so much energy to go around for this old person. I was amazed at how big they were at Tom Burseens. I know he adds some stuff to his soil, plus he is always digging and moving around stuff. Sometimes they just like to be aerated some. I'm sure they would like a little food from time to time, but they bloom and that is all I care about. Well they bloom if they have enough cold here.
Dot
