I have half a dozen rhubarb 'Timperley Early' at my allotment. I stop picking the stalks in late June/early July then I just ignore them for the rest of the year. In the winter the foliage dies and disappears into the ground. I do try to surround them with a thick layer or well rotted compost in the winter, and in the picking season I will try to water them if they are looking a bit dry. Apart from that I tend to leave thenthem to do their own thing.