They are supposed to die out like you said, Frank, but can start growing again if the tree peony is planted too shallow or the graft didn't take. I would be very concerned about the viability of any tree peony that had herbaceous roots for more than the first year or two. That nurse root should be dying as the tree peony grows its own roots. If the herbaceous roots are doing well enough to put up more than a few straggler leaves you'd have a problem with overcrowding your tree peony roots at best, tree peony roots not forming at all at worst. If it were me and I was seeing herbaceous leaves with my tree peony that had been in the ground long enough to form its own roots I'd be digging that thing up and dealing with it permanently in the fall. I haven't had to make that call on any I have yet, got really lucky with the first ones I planted because I certainly didn't know to plant them deeper.
Debra, if the picture does show the actual graft line on your tree peony I'd plant it deeper at some point. Does anyone out there have a method for dealing with too shallow roots that works other than digging it up and re-planting? Would mounding around the root work or would that just kill the plant? I'd love to know the answer for my own peony education. Also, for my own selfish reason--it's !X#D% dull in Colorado this time of year, this conversation is relieving the monotony!
