Thereare many flowers that go by the name lily. But only a few are actually lilies. To be a true lily, a flower must belong to the Liliaceae family, a plant species that has been the subject of botanical disagreement for many years.

Plants within the Liliaceae and another flower family—theAmaryllidaceae—are often mistaken for the same family. So how can you pick out a real lily from the bunch? The British Royal Horticultural Society upholds this traditional classificationlants with a superior ovary are considered part of the Liliaceae family—true lilies—and plants with an inferior ovary are part of the Amaryllidaceae family.

With this distinction in mind, here is an A to Z of true lilies; see how many are in your garden:

• Lily of the Nile (Agapanthus africanus)
• Peruvian lily (Alstroemeria aurea and its hybrids)
• Lily of the valley (Convallariamajalis)
• Foxtail lily (Eremurus x isabellinus)
• Glory lily (Gloriosa superba)
• Trout lily (Erythronium americanum)
• Daylily (Hemerocallis species and hybrids)
• Checkered lily (Fritallaria meleagris)
• Plantainlily (Hosta species and hybrids)
• Mountain lily (Lilium auratum)
• Meadow lily (Lilium canadense)
• Martagon lily (Lilium martagon)
• Hybrid trumpet lilies and Aurelian hybrids (L. henryi and hybrids of other Asiatic species)
• Lily turf (Liriope muscari)
• Red hot poker (Kniphofiax praecox hybrids)
• Solomon’s seal (Polygonatum  species)
• Toad lily (Tricyrtis species)
• Wood lily (Trillium species)
• Death camas (Zigadenus species)

 
And now for the lily imposters: none of these so-called lilies are actually the real deal (but that doesn't mean you should admire them any less):

• Calla lilies, one of the most popular cut flowers, are not true lilies at all. Instead, they are exotic-looking planst belonging to the family Araceae in the genus Zantedeschia. The lesser known wild,or “true,” calla lily (Zantedeschia aethiopica, syn. Calla aethiopica) is awoodland plant.
• Canna lilies are in the family Cannaceae; many in the trade are Canna x generalis hybrids.
• The blackberry or leopard lily (Belamcanda chinensis) belongs to the family Iridaceae.
• There is also a newcomer called the candy lily, ahybrid of the genera Belamcanda and Pardanthopsis.
• The Jacobeanor Aztec lily (Sprekelia formosissima) is the only plant in the genus Sprekelia, in the family Amaryllidaceae. The Belladonna lily (Amaryllisbelladonna), Kaffir lily (Clivia species), Amazon lily (Eucharis x grandiflora), Sky blue lily (Ixiolirion species), Fairy lily (Zephyranthes rosea), Magic lily (Lycoris squamigera) and the well-known Amaryllis (Hippeastrum hybrids) are also in the Amaryllidaceae family.

If it is true that “a rose by any other name would smell as sweet," it is equally true that many plants designated by the name “lily” are valuable additions to the garden, whether they are members of the Liliaceae family or not.

Recommended Reading: 

 The Well-Tended Perennial Garden 

Encyclopedia of Perennials