(Rheum rhabarbum) Central Asian native that has been grown in Europe for centuries, for medicinal and food use. At its best in cooler summers with cold winters, but can be grown in warmer climates with some afternoon shade. Seeds are started indoors or outside in a nursery bed, and transplanted to their final location. Mature rhubarb plants are quite large, so space them at lest 2 feet apart. Requires rich soil and ample moisture. Harvest the succulent stalks starting the second year.