|This perennial thrives in temperate climates and is tolerant of many soil types as long as nitrogen levels are average. Plant tubers in spring when ground is workable. Break tubers apart so that they are the size of an egg, being sure that each piece has several vigorous looking buds. Plant 5 inches deep, 1 foot apart. When plants are about 1 foot tall, mound soil around base at least 6 inches high to add support. You may prefer to stake plants. In late summer, cut stalks back to 5 feet high, removing any flowers. Once leaves start to yellow and shrivel, cut all the way back to ground. Tubers may stay in the ground until you are ready to use them (lasting up to 20 weeks).