I recently made some candied kumquats and used a progressively sweeter syrup over several days. Syrup is boiled then poured over the kumquat pieces - no boiling of the kumquats. It's possible that would work for rhubarb without destroying the cell walls.

Thanks John and Pastry Girl.
I did the kumquats the same way...try them in vanilla ice cream. So good. I bet the candied Rhubarb would have much the same effect.
I'll just wash the stuff, get the DH to slice them (my manual dexterity is blown), and then into the syrup they go.
Friend back home...east central Ontario...has a ring to it, doesn't it?...informs me that green things are just poking up a tiny bit. It's been a cold April and we are up several hundred feet from the environs.
Oh, John...you poured the syrup over the kumquat, but you didn't heat them at all? Not even on low in a crock pot? I did mine on low in my crock pot.