It is not too much of an exaggeration to make a case that rhubarb, that earliest of springtime perennials, is the ultimate New England plant. Just consider: rhubarb is both hardy and stubborn, and once established in our rocky soil, it is there for the duration. A traipse around Maine fields may well turn up the sites of once-proud farmhouses, all but vanished except for the foundation stones and the rhubarb patch.