I received an imperialis tuber early this spring (from Van Bourgoundien I believe) and potted it up indoors in a 4-inch fiber pot. A growth shot up 18 inches but when planted outside in May has since refused to grow. Can I dig it up before frost and save the tuber by continuing to grow it near a sunny window? Bonaventure Magrys Cliffwood Beach, NJ USA zone 6-7