Answer: The true bulb lilies (Lilium) such as the Asiatic Hybrids and the Orientals and the so-called tiger lilies can be left in the ground year round. Daylilies (Hemerocallis) can also be left in the ground year round. Lily-of-the-valley (Convalleria majalis) is also a hardy perennial that can stay in the ground. Off the top of my head, I can't think of a lily that needs to be dug each year except the plant commonly called calla lily (Zantedeschia) which must be brought in for the winter.
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