Flora of North America species comparison

Throughout most of modern botanical history this Chinese lily has been known as Lilium tigrinum, but recent nomenclatural reassessment affirms that Thunberg’s description, published sixteen years earlier than Ker Gawler’s, applies to this species. Though many North America species are known vernacularly as tiger lilies, the name is properly applied only to this one. Along with L. candidum, it is considered to be among the earliest domesticated lilies (H. D. Woodcock and W. T. Stearn 1950), no doubt because it is handsome, easy to grow, and the bulbs are edible and substantial. It is widely planted in North America, usually as a sterile triploid that is best propagated from the bulbils.

Perhaps the hardiest garden lily, Lilium lancifolium is a widespread but sporadic garden escape, and roadside lilies near habitation in eastern and northeastern North America are often this species. Despite its general use in gardens, it seems to be naturalized only in the better-watered eastern portion of the continent.

In North America, the tiger lily is rather easily diagnosed by its truly lanceolate and widely sessile alternating leaves that bear dark bulbils on the upper stem. The mature buds are usually high-shouldered and taper rather evenly to a flattish apex with three greenish, terminal, rounded processes. No native lily consistently displays any of these features.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The largest Lilium east of the Rocky Mountains and the commonest over most of its range, the Turk’s-cap lily is a familiar sight throughout much of the southern Appalachians and along the northern Atlantic coastal plain. Flowers are rather variable; those in the north are sometimes floridly colored with dark purple bases on the perianth parts. The single report from Vermont (F. C. Seymour 1993) remains unconfirmed; however, recent collections from Washington Parish in Louisiana, Perry County in Missouri, and Bamberg County in the coastal plain of South Carolina extend the range of this species.

Lilium superbum shares distinctive features with L. michauxii, L. pyrophilum, and L. iridollae that indicate a close relationship and are diagnostically useful, namely paired ridges on the backs of the sepals and buds that are triangular in cross section. None has the red style characteristic of the other eastern pendent lily clade (L. michiganense, L. canadense, and L. grayi) centered to the northwest, and only L. iridollae sometimes has the leaf margins and veins roughened abaxially as is characteristic of L. canadense and its close relatives.

Common inheritance of a suite of unique, derived features and peripheral allopatric distributions suggest that Lilium pyrophilum and L. iridollae may be geographical isolates of broadly distributed L. superbum ancestral stock; both restricted species occur in specialized wetland habitats. Geography aside, the three are unequivocally distinguished only by various combinations of leaf and bulb characteristics, flower color, habitat, and blooming time. However, the overall degree of separation is comparable to that between many other species in the genus. Lilium superbum blooms the earliest, is the largest, and has the most numerous and largest flowers, and the long, narrow leaves in many whorls are distinctive. Lilium michauxii overlaps in range with these three species but is easily separated morphologically and ecologically.

Lilium superbum is pollinated primarily by the swallowtail butterflies that are common within its range, among them the spicebush (Papilio troilus Linnaeus, family Papilionidae), pipevine (Battus philenor Linnaeus), and eastern tiger (Papilio glaucus Linnaeus). Great spangled fritillaries [Speyeria cybele (Fabricius), family Nymphalidae] also visit the Turk’s-cap lily (R. M. Adams and W. J. Dress 1982).

(Discussion copyrighted by Flora of North America; reprinted with permission.)