Lilium

Herbs, perennial, bulbose. Bulbs whitish, rarely yellowish or purplish, often stained brown, erect and ovoid (hereafter “ovoid”), irregular and chunky (“chunky”), slanted in ground and ± elongate (“subrhizomatous”), or horizontally elongate (“rhizomatous”), sometimes branching if rhizomatous, rarely if not, 1.4–11.7 × 1.3–19 cm, 0.1–3 times taller than long, annual growth usually obscure; scales (modified leaves) numerous, fleshy and starchy, usually densely covering rhizomes, rarely bearing leaf blades known as basal leaves or their abscission scars, often notched or segmented, longest 0.8–11.9 cm; roots on each bulb either contractile and concentrically wrinkled and thick (to 5 mm), or for nutrition and thinner, fibrous. Stems erect, green, sometimes purple, rarely glaucous, to 3.1 m, ± glabrous, often with adventitious stem roots above bulb. Buds usually rounded in cross section, sometimes ± triangular. Leaves numerous, usually ± evenly distributed along stem, rarely concentrated proximally, scattered or more commonly in 1–12(–24) whorls with some scattered at stem base and apex, 3–20(–40) leaves per whorl, sessile, drooping at tips to ascending, 1.7–29 × 0.2–5.6 cm, 1.6–34 times longer than wide; blade green and somewhat lighter abaxially, rarely paler, linear, lanceolate, elliptic, or obovate, sometimes oblanceolate, especially in proximal leaves, often somewhat lanceolate in distal leaves, margins entire, undulate or not, usually glabrous and smooth or occasionally slightly papillose, sometimes roughened abaxially by ± deltoid epidermal spicules, apex acute to obtuse or rarely acuminate; principal veins usually 3, usually glabrous and smooth abaxially, sometimes with ± deltoid epidermal spicules, rarely impressed adaxially. Inflorescences maturing acropetally, terminal, racemose or umbellate (in small plants), usually open, bracteate, 1–25(–45)-flowered; bracts usually 1–2 per flower, often with one lanceolate and very wide and the other linear or filiferous. Flowers pendent, nodding, horizontal, ascending, or erect, radially or slightly bilaterally symmetric, fragrant or not; perianth campanulate, funnelform, or with sepals and petals strongly reflexed in form of a “Turk’s-cap”; sepals and petals usually differentiated, sometimes indistinctly so, recurved or reflexed, distinct, orange, red, yellow, pink, or white, usually with adaxial magenta or maroon spots concentrated in proximal 1/2–2/3, ± lanceolate and narrowed or rarely clawed, glabrous (pubescent strip at base in L. lancifolium), nectaries present on each but often more developed on sepals, basal, green, usually hidden but occasionally exposed and forming visible green star at adaxial base of perianth; sepals 3, occasionally ridged abaxially, 3.1–12 × 0.6–2.6 cm, apex usually acute; petals 3, ridged abaxially, with 2 adaxial longitudinal median rounded ridges, 3–11.2 × 0.6–3.4 cm, apex usually acute, often more widely than sepal apex; stamens 6, opposite sepals and petals, distinct, included to strongly exserted; filaments ± parallel to style or spreading, diverging to 31° from flower axis, color variable but usually pale green or nearly translucent; anthers versatile, color variable, usually purplish, becoming darker, oblong, 0.3–2.6 cm; pollen cream, yellow, peach, tan, orange, rust, or brown, usually becoming lighter; pistil compound, 3-lobed, 3-locular, oblong, 2.1–10.5 cm; ovary superior, 0.8–3.5 cm, axile placentas 6, ovules as many as seeds, a few developing without embryos; style initially parallel to flower axis, usually elongating and curving toward periphery, usually pale green, round in cross section; stigma 3-lobed, hollow in older flowers; pedicel not articulate, 0.8–32 cm. Fruits erect, green maturing to brown, capsular, 3-valved, not strongly winged, ± oblong-obovate, 1.5–7.7 × 0.8–3.3 cm, 1.1–4.8 times longer than wide, base constricted, dehiscence loculicidal. Seeds 67–330, light brown with darker ovate embryo in center, 6-ranked, flattened into 60° wedge, verrucose. x = 12.

Distribution

Temperate Northern Hemisphere south to mountains of Asian tropics.

Discussion

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.

Selected References

Adams, R. M. and W. J. Dress. 1982. Nodding Lilium species of eastern North America (Liliaceae). Baileya 21: 165–188.

Elwes, H. J. 1880. A Monograph of the Genus Lilium. London.

Hayashi, K. and S. Kawano. 2000. Molecular systematics of Lilium and allied genera (Liliaceae): Phylogenetic relationships among Lilium and related genera based on rbcL and matK gene sequence data. Pl. Spec. Biol. 15: 73–93.

Nishikawa, T. et al. 1999. A molecular phylogeny of Lilium in the internal transcribed spacer region of nuclear ribosomal DNA. J. Molec. Evol. 49: 238–249.

Skinner, M. W. 1988. Comparative Pollination Ecology and Floral Evolution in Pacific Coast Lilium. Ph.D. dissertation. Harvard University.

Stewart, R. N. 1947. The morphology of somatic chromosomes in Lilium. Amer. J. Bot. 34: 9–27.

Synge, P. M. 1980. Lilies: A Revision of Elwes’ Monograph of the Genus Lilium and Its Supplements. New York.

Tamura, M. N. 1998c. Liliaceae. In: K. Kubitzki et al., eds. 1990+. The Families and Genera of Vascular Plants. 4+ vols. Berlin etc. Vol. 3, pp. 343–353.

Woodcock, H. D. and W. T. Stearn. 1950. Lilies of the World: Their Cultivation and Classification. London.

Lower Taxa

Lilium bolanderi, Lilium canadense, Lilium catesbaei, Lilium columbianum, Lilium grayi, Lilium humboldtii, Lilium iridollae, Lilium kelleyanum, Lilium kelloggii, Lilium lancifolium, Lilium maritimum, Lilium michauxii, Lilium michiganense, Lilium occidentale, Lilium pardalinum, Lilium parryi, Lilium parvum, Lilium philadelphicum, Lilium pyrophilum, Lilium rubescens, Lilium superbum, Lilium washingtonianum

Key

1	Flowers nodding to erect; perianth widely campanulate or funnelform; sepals and petals mostly recurved but not reflexed (except reflexed or rolled in L. maritimum; weakly reflexed in L. parvum).	> 2
1	Flowers pendent (to nodding in L. columbianum); perianth Turk’s-cap-shaped (campanulate in L. canadense); sepals and petals reflexed (somewhat recurved in L. canadense).	> 10
2	Sepals and petals distinctly clawed; inflorescences rarely more than 3-flowered; flowers erect.	> 3
2	Sepals and petals not distinctly clawed; inflorescences occasionally 1-flowered, but usually 2–many-flowered; flowers nodding to erect (if erect, at least some horizontal to ascending on each plant).	> 4
3	Sepal and petal apices very narrowly acute, sepals 8.2–12 cm; leaves scattered; se United States.	Lilium catesbaei
3	Sepal and petal apices obtuse to acute, sepals 4.9–8.2 cm; leaves whorled, or if scattered, then with at least 1 distal whorl, or infrequently entirely scattered; widespread.	Lilium philadelphicum
4	Sepals and petals white, often aging purple or pink; flowers ± horizontal to erect.	> 5
4	Sepals and petals yellow, orange, red, or magenta, rarely pinkish, and if so, not darkening significantly with age; flowers nodding to ascending.	> 6
5	Sepals 4.3–6.6 cm; flowers ascending to erect; bulb scales always unsegmented; nw California.	Lilium rubescens
5	Sepals (6.1–)6.7–11.3 cm; flowers ± horizontal; bulb scales often notched but not fully segmented, or segmented; mountains of n California, Oregon.	Lilium washingtonianum
6	Sepals and petals bright yellow; sepals 7.7–10.7 cm; mountains of s Arizona, s California.	Lilium parryi
6	Sepals and petals red, orange, magenta, or pink, rarely pale yellow; sepals 3.1–5.6 cm; West Coast or Appalachians.	> 7
7	Leaves 1.8–7.1 cm, blade noticeably glaucous, margins nearly always undulate; bulbs ± ovoid, thus a species of dry ground; bulb scales unsegmented, longest always 3 cm or longer; flowers nodding to horizontal; sepals 3.1–4.7 cm; Klamath Mountains of Oregon and California.	Lilium bolanderi
7	Leaves 3.6–17.7 cm, blade not noticeably glaucous, margins never undulate; bulbs rhizomatous, thus species of moist or wet places; bulb scales variable, usually at least a few segmented, longest shorter than 3 cm (rare exceptions in large plants); flowers nodding to ascending; sepals 3.2–5.6 cm; w United States or Appalachians.	> 8
8	Leaf veins and margins noticeably roughened abaxially with ± deltoid epidermal spicules; rhizomes with scaleless sections between annual bulbs; flowers nodding; sepals 3.2–5.6 cm; style red; s Appalachians.	Lilium grayi
8	Leaf veins and margins ± smooth abaxially; rhizomes continuously scaly; flowers nodding to ascending; sepals 3.2–5 cm; style green; n California.	> 9
9	Flowers nodding or rarely horizontal; sepals and petals reflexed or rolled 1/2–4/5 along length from base, red or red-orange; sepals 3.4–5 cm; capsules 2.4–4.1 cm; bulb scales usually unsegmented, a few 2-segmented; extreme coastal n California.	Lilium maritimum
9	Flowers ± horizontal to ascending; sepals and petals somewhat recurved but not strongly reflexed, orange or yellowish proximally, darker (orange, red-orange, red, or rarely pinkish) on distal 2/5, occasionally uniformly light orange or rarely yellow; sepals 3.2–4.2 cm; capsules 1.6–2.7 cm; bulb scales (1–)2–3(–4)-segmented; Sierra Nevada.	Lilium parvum
10	Leaves scattered; axillary bulbils present on distal leaves; introduced, often persisting near dwellings; c and e North America.	Lilium lancifolium
10	Leaves whorled, though distal and proximal may be scattered; axillary bulbils entirely absent from leaves; endemic; geographically scattered.	> 11
11	Sepals and petals pink or less often white, with median longitudinal yellow stripe, often aging deep pink; sepals 3.4–7.2 cm; mountains of nw California and sw Oregon.	Lilium kelloggii
11	Sepals and petals yellow, orange, or red; sepals 3.4–10.4 cm; geographically scattered.	> 12
12	Leaf blade noticeably pale abaxially, texture noticeably fleshy, oblanceolate, occasionally obovate; flowers strongly fragrant; s and se United States.	Lilium michauxii
12	Leaf blade lighter green but not pale abaxially, texture not noticeably fleshy, shape variable; flowers odorless or mildly fragrant; geographically scattered.	> 13
13	Bulbs subrhizomatous to ± ovoid, thus species of drier ground; longest bulb scales always longer than 3 cm; sepals and petals orange or yellow.	> 14
13	Bulbs rhizomatous, thus species of moist, wet, or low places; longest bulb scales shorter than 3 cm (with rare exceptions in large plants); sepals and petals yellow, yellow-orange, or reddish.	> 15
14	Pistil 2.4–3.7 cm; sepals 3.4–7.1 cm; anthers 0.5–1.3 cm; capsules 1.1–2 cm wide; n California to Montana, British Columbia.	Lilium columbianum
14	Pistil 4.6–7.1 cm; sepals 5.2–9.8 cm; anthers 1.1–1.9 cm; capsules 1.8–3.3 cm wide; Sierra Nevada and s California.	Lilium humboldtii
15	Rhizomes continuously scaly; w of Rocky Mountains.	> 16
15	Rhizomes with scaleless sections between annual bulbs; e of Rocky Mountains.	> 18
16	Flowers mildly fragrant; sepals and petals yellow or yellow-orange; sepals 4.3–5.7 cm; anthers 0.3–0.6 cm; pistil 2.6–3.4 cm; capsules 1.5–2.9 cm; Sierra Nevada above 2200 m.	Lilium kelleyanum
16	Flowers almost never fragrant; sepals and petals ± two-toned with green, yellow, or orange proximally, darker orange to red on distal 1/5–2/3 (except ± uniformly orange or yellow-orange in L. pardalinum subsp. wigginsii); sepals 3.5–10.4 cm; anthers 0.5–2.2 cm; pistil 3–7.5 cm; capsules 2.1–5.7 cm; California and Oregon below 2000 m.	> 17
17	Sepals and petals green to yellow proximally, red to maroon (to orangish) distally, conspicuously green abaxially on proximal 2/5–1/2; sepals 4.4–8.1 cm; filaments ± parallel to style, diverging only 4°–12° from axis; rhizomes never branched; extreme coastal n California and s Oregon.	Lilium occidentale
17	Sepals and petals yellow to orange proximally, orange to red distally (except subsp. wigginsii), conspicuously green abaxially only on proximal ± 1/5; sepals 3.5–10.4 cm; filaments spreading from style, diverging 7°–22° from axis; rhizomes usually branched; California and s Oregon.	Lilium pardalinum
18	Style red, at least distally, or brightly colored like sepals and petals; sepals not ridged abaxially; buds rounded in cross section; leaf veins and margins noticeably roughened abaxially with ± deltoid epidermal spicules; bulbs usually yellowish.	> 19
18	Style pale green; sepals with 2 parallel, often faint abaxial ridges; buds ± triangular in cross section; leaf veins and margins ± smooth abaxially (except often rough in Lilium iridollae); bulbs whitish.	> 20
19	Sepals and petals reflexed; filaments parallel to style at first, then widely spreading, diverging 13°–23° from axis; stamens moderately exserted; midwestern North America.	Lilium michiganense
19	Sepals and petals somewhat recurved; filaments ± parallel to style, barely spreading, diverging 4°–6° from axis; stamens barely exserted; e North America.	Lilium canadense
20	Rhizomes 9.6–18 cm, with 3–4 annual bulbs, scaleless sections between bulbs 2.7–5.4 cm; bulb-scale leaves or their abscission scars present; inflorescences 1–4-flowered; sepals and petals yellow-orange or yellow; coastal plain in Alabama and w Florida.	Lilium iridollae
20	Rhizomes 5.2–10.2 cm, with 2(–3) annual bulbs, scaleless sections between bulbs 0.3–3.8(–4.6) cm; bulb-scale leaves or their abscission scars absent; inflorescences 1–22-flowered; sepals and petals orange or reddish; s and e United States.	> 21
21	Stems 1.2–2.8 m; leaves usually ± evenly distributed along stem, usually horizontal and drooping at tips, in 6–24 whorls of 3 or more, 7.1–26.1 cm, 4–18 times longer than wide; inflorescences 1–22-flowered; sepals and petals usually red-orange; s and e United States.	Lilium superbum
21	Stems 0.6–1.6 m; leaves often concentrated proximally, usually ascending, in 0–12 whorls of 3 or more, 2.3–10.3(–12.2) cm, 1.6–7.6(–10.3) times longer than wide; inflorescences 1–7-flowered; sepals and petals variable, usually red-orange or dusky red, often somewhat pale; sandhills of Virginia and the Carolinas.	Lilium pyrophilum