Flora of North America species comparison

This is the only fragrant native lily east of the Rocky Mountains. The Carolina lily occurs in well-drained soils, while the three closely related congeners with which it is sympatric, Lilium superbum, L. iridollae, and L. pyrophilum, occur in either wetlands or moist woods. Where it occurs with L. superbum, as it often does along roadsides, L. superbum grows in the adjacent depressions and L. michauxii on the bank. Among its close relatives, its small stature, broad petals, and consistently oblanceolate leaves with undulate margins and acuminate tips are diagnostic. In these features it rather resembles several of the western taxa, especially smaller plants of L. rubescens; vegetative or fruiting herbarium material of the two can be confused. In L. michauxii the leaves are noticeably fleshy and pale abaxially, relatively few in number, and, perhaps because whorls are also few (commonly 2–4), the leaves seem concentrated near the middle of the stem.

This species is less common in the southwestern portion of its range, where it is sometimes encountered in vegetative form in shaded settings that preclude rapid growth and flowering.

Like the other southeastern pendent-flowered lilies, the Carolina lily is pollinated by large swallowtail butterflies including the eastern tiger (Papilio glaucus Linnaeus, family Papilionidae).

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

Species ca. 100 (22 in the flora).

Perennial herbs of unsurpassed beauty and great commercial significance, the true lilies have been celebrated since time immemorial. Lilium candidum is the Madonna lily of biblical importance; L. longiflorum is the Easter lily. In China, lilies have been cultivated, eaten, and used medicinally for at least 2000 years (S. G. Haw 1986). Today, lilies are one of the mainstays of the worldwide horticultural bulb trade and many species are available. Usually these “species lilies” are susceptible to various diseases and cultural problems that render them difficult to maintain in gardens. Thousands of hybrids have been developed and about 6000 are registered, the best of which combine the delicate features of their wild relatives with disease resistance and hardiness. By and large, these hybrids predominate among the lilies grown in home gardens in North America, though the exotic L. lancifolium (tiger lily; China) is also widely grown, as to a lesser degree are several native species including L. pardalinum, L. canadense, and L. superbum. The other North American lilies rarely thrive in gardens, especially outside their native ranges, and most have suffered from excessive collecting. None should be removed from the wild.

The true lilies are distributed circumboreally, particularly in mountainous regions, and reach their southern limit in the tropical mountains of the Philippines and India. Eastern Asia and North America are the centers of highest worldwide diversity, with about 60 and 21 species respectively. The closest relatives are found in eastern Asia, where Lilium originated, in the genera Fritillaria, Nomocharis Franchet, Notholirion Wallich ex Boissier, and Cardiocrinum (Endicher) Lindley (H. D. Woodcock and W. T. Stearn 1950); many species now placed in these related genera have resided in Lilium at one time or another. The boundary between Lilium and Nomocharis has been particularly fluid taxonomically, and some recent molecular classifications (M. F. Fay and M. W. Chase 2000) include Nomocharis in Lilium. Of the closest relatives, only Fritillaria occurs in North America. It is distinguished from Lilium by smaller stature and shorter perianth parts (to ca. 4 cm), and by a small bulb usually consisting of a few large scales and numerous rice-grain-sized offset scales.

The 21 species of Lilium that are native to North America are derived from Asian stock, but since a suitable infrageneric classification for our species has not been developed, none is presented here. Nevertheless, there are several groups of evolutionary and taxonomic significance. Lilium philadelphicum and L. catesbaei are the only two North American lilies with erect flowers, highly clawed perianth parts, and spots confined to well-defined nectar guides. These two species almost certainly represent a single introduction from Asia (K. Hayashi and S. Kawano 2000; T. Nishikawa et al. 1999), the rest of the taxa probably another (M. W. Skinner 1988). The 12 species of the Pacific Coast fall into two groups. Species 4–9 are plants of usually dry ground with ± ovoid or oblique bulbs; this group is basal to those remaining, and is not monophyletic. Species 10–15 are plants of moist or wet places with rhizomatous bulbs that frequently branch; these apparently originated from within the dry-ground group (M. W. Skinner 1988). Species 16–22, the pendent-flowered eastern lilies, appear to have their closest relationship with L. pardalinum in the west, but within themselves form a coherent group of two rather well-defined alliances. Species 16–19 are characterized by southern and eastern distributions, buds that are triangular in cross section, and sepals with two abaxial longitudinal ridges. Species 20–22 occupy more northern distributions, and have in common roughened leaves due to spicules on the leaf margins and abaxially on the veins, usually yellowish bulbs, and red styles. If species 16–19 and 20–22 are considered separately, complementary allopatric or parapatric distributions—usually with hybridization in zones of contact—are the norm within all of the groups except for the one that contains species 4–9.

Most lilies are largely self-incompatible, and cross-pollination is required for seed set (J. S. Davis 1958). The flowers are weakly protandrous: pollen is offered upon anthesis, and then over time the pistil elongates, the style generally curves toward the periphery (particularly in pendent-flowered species), and the stigma enlarges. Nectar is offered especially from the sepal nectaries to reward insect pollinators, and also hummingbirds in North America. Phylogenetic analysis (M. W. Skinner 1988) suggests that the original pendent lilies to colonize North America were butterfly-pollinated, and other pollination syndromes involving moths and hummingbirds evolved in situ via pollinator mediation.

Identification of Lilium herbarium specimens is often difficult since bulbs are rarely collected and crucial features such as flower color, shape, and orientation are altered in pressed material. Leaf characters including shape, margin, and vestiture are sometimes diagnostic, and flower and anther size are frequently useful, but it is often necessary to resort to comparison of distributions during specimen identification. The keys and descriptions presented here are based on live plants, and anther measurements were taken following dehiscence. Descriptions of the flowers refer to the adaxial surface unless otherwise noted. A whorl or partial whorl consists of three or more leaves arranged cyclically on the stem, and bulb dimensions are given as height × length along the horizontal axis.

Regardless of their shape, the bulbs of the North American species are actually radially asymmetrical, slowly growing, scaly rhizomes. In some (e.g., L. kelloggii and L. rubescens), lateral growth is very slow and the bulb remains upright and more or less ovoid. In others, such as L. philadelphicum, the growing point appears to rotate around the underground stem, and the bulb remains compact but irregular. In L. washingtonianum the bulb is somewhat horizontally extended and slanted in the ground with the growing end deeper; this condition is termed subrhizomatous. In the majority of our species, however, the rhizome extends horizontally and the flowering stem moves incrementally each year; these bulbs are termed rhizomatous. Only in some of these rhizomatous lilies, for example L. pardalinum and L. superbum, do the bulbs branch often and evenly to produce two new plants. Other bulb types branch only rarely and irregularly. In the more extended bulb forms it is sometimes possible to count the partially visible annual stem scars to derive plant age, but this is usually an underestimate since the dying end of the bulb continually deteriorates.

Several species of Asian or European origin are sporadically naturalized following escape from cultivation, but none strays far or is widespread or common enough to be considered a pest. Lilium bulbiferum Linnaeus (orange lily; Europe) is tall, with linear alternate leaves and 1–3(–20) erect, widely campanulate orange flowers; the perianth parts are recurved, clawed, and conspicuously papillose adaxially at the base. It is somewhat similar to native L. philadelphicum but for its papillose perianth and axillary bulbils, though the latter are not always present. It is occasionally found outside cultivation in temperate northeastern North America (Quebec, Ontario, and New Brunswick) and sparingly in the intermountain west in Utah (J. T. Kartesz and C. A. Meacham 1999). Lilium candidum Linnaeus (Mediterranean) is tall (1–2 m), with many lanceolate, ascending leaves and pure white, campanulate flowers of modest size (perianth parts to 8 cm) that are fragrant and horizontal to ascending on the stem; it is naturalized in two counties in Pennsylvania (A. F. Rhoads and W. M. Klein 1993). Lilium martagon Linnaeus (martagon lily; Eurasia) shares with many of the native species both whorled leaves and Turk’s-cap flowers, but the latter are small (perianth parts to 3.5 cm), very numerous, and purple or sometimes white. It is weakly naturalized in Michigan near Ann Arbor, and perhaps in Quebec (H. J. Scoggan 1978–1979, part 2). Several similar Asian lilies with scattered leaves and long, funnelform white flowers are reportedly naturalized in the southeastern United States; careful examination is required to identify them correctly. Lilium longiflorum Thunberg (Easter lily; Japan) is the common white lily of the florist trade; it is the most widely cultivated and commercially important lily. Plants are short (to 1 m), the leaves lanceolate and to 18 × 1.5 cm, and the pure white flower is fragrant and larger than in any of our native species; the perianth parts are 13–18 cm and glabrous at the base adaxially. It has been recorded from Utah (S. L. Welsh et al. 1993) and Florida. Lilium formosanum Wallace (Formosa lily; Formosa) is tall, with numerous long (to 20 cm), linear leaves of dark, lustrous green. The 1–2(–10) horizontal flowers are delicately fragrant, white, and usually suffused with wine-purple abaxially; the perianth parts are 13–20 cm long and basally papillose adaxially. The Formosa lily is evidently infrequently naturalized and has been reported from Louisiana and Florida, although most if not all of these records—like the two records of L. regale E. H. Wilson from Alabama (R. Kral 1981)—represent the next species. Lilium philippinense Baker (Philippine lily; Philippines) is similar to L. formosanum but with a thinner, longer floral tube. The delicately fragrant flower is white, occasionally streaked with green and red basally, and is the largest in the genus; the perianth parts are 18–25 cm and basally papillose. It is reported from one location in Kentucky (E. T. Browne Jr. and R. Athey 1992) and is becoming well established in parts of Florida, especially near Tallahassee.

Native Americans relied on the bulbs of many species of Lilium for food and medicine, and preparation varied widely (D. E. Moerman 1986). From L. canadense bulbs the Cherokee made flour and then bread for use during famine. In British Columbia, the Thompson Indians mixed L. columbianum bulbs with salmon roe and this was boiled and eaten as a favorite dish. In Saskatchewan, the Cree dried the bulb scales of L. philadelphicum as a snack. Otherwise, the bulbs were steamed, dried into cakes for winter use, baked in an earth oven, or made into soup. Lilies were equally versatile as medicine, and the mashed bulbs were variously employed in the treatment of spider bites, cuts and bruises, fever, coughs, consumption, stomach ailments, and rheumatism. Contemporary medical use seems to be largely limited to L. lancifolium, the bulbs of which are used to treat a variety of internal discomforts, including those associated with menstruation and menopause.

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