Answer: Your plant is not Carex hachijoensis, but Carex morrowii var. aureo-variegata. Your plant, the dwarf variegated Japanese Carex called 'Old Gold' is more widely banded yellow than 'Variegata' but some plants under this name are not distinct and therefore there can be some confusion. Carex morrowii 'Old Gold' is hardy to USDA zone 5 and should be just fine in your garden.
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