After those leaves die off and trim them and dig them up you have to amend your soil, dig the sandy soil out and mix it with mulch and well rotted manure and new vitamin dirt....replant your tubers 3 to 4 ft apart as they like good air circulation about 1 1/2 to 2" deep add 1 cup bonemeal in the mix...they like loomy ph neutral soil, part to full sun zone 3 to 8, good drainage and they can last up to 100 years. They like cold weather so don't mulch in the winter. The best time to do this is fall to late fall.