Rhubarb is what is known as a gross feeder ... It needs plenty of muck and will not thrive in a container. My granddad used to empty the chamber pot out of the window onto his ... Beautiful stuff ! If you want to force it, a portion should be dug up and left over winter out in the frost, then it is possible to pot up and cover ,to keep in the dark, with a bottomless bin or suchlike to produce tender stems. This process will exhaust the crown which can however be replanted, but let it grow without picking for a year or two to recover.