Herbs, perennial, scapose, from ovate to elongate bulbs, sometimes with small, beadlike segments of short, persistent rhizome attached; several species producing additional bulbs as sessile bulbels or at the ends of slender stolons or vertical droppers, these species typically flowering more sparingly than those without extensive vegetative reproduction. Leaves 2 (1 in nonflowering plants), basal, ± petiolate; blade green or mottled with purple, brown, or white, lanceolate to ovate (wider if solitary), flat to folded, 6–60 cm, glaucous in a few species, glabrous, base narrowed gradually or abruptly to petiole, margins entire or sometimes wavy. Scape green or sometimes reddish, typically elongating in fruit. Inflorescences terminal, racemose, 1–10-flowered. Flowers showy, usually nodding, sometimes held laterally or erect; tepals 6 (as few as 4 in E. propullans), spreading to reflexed, distinct, similar, white, yellow, pink, or violet, often with basal zone of yellow or other colors, lanceolate to ovate, inner tepals auriculate at base in many species, auricles appressed to ovary and forming sac- or pocketlike hollows on adaxial surfaces; stamens 6; filaments generally slender; ovary superior; style 1, abruptly attached to ovary (or forming a beak in E. rostratum); stigma unlobed or 3-lobed, lobes recurved to erect. Fruits capsular, erect, obovoid to oblong, apex rounded, truncate, or umbilicate (beaked in E. rostratum), dehiscence loculicidal. Seeds brown, ± angular, ± ovoid. x = 11, 12.

Distribution

All North American, except for the Eurasian Erythronium dens-canis Linnaeus and its segregates E. caucasicum Woronow, E. japonicum Decaisne, and E. sibiricum (Fischer & C. A. Meyer) Krylov, north temperate in forest and montane meadow habitats, one species (E. mesochoreum) in prairies.

Discussion

Species ca. 27 (23 in the flora).

Erythronium is a well-marked and distinctive genus closely related to Tulipa. In North America, Erythronium consists of distinct eastern and western groups, the former clearly having an affinity with species of the Old World. Most of the species have attractive and showy flowers, and several are well suited for naturalizing in woodland gardens.

Pressed specimens tend to fade, so leaf and flower colors and markings should be recorded on specimen labels at the time of collection. The orientation of flowers and fruits should also be recorded, and it is useful to collect bulbs of both flowering and nonflowering plants when this will not damage a population. Bulbs of Erythronium species are often more than 10 cm deep. Collectors should press flowers so that the shape of the style, stigmas, filaments, and petal bases can be observed later.

Species of western North America (Rocky Mountains westward) and eastern North America (Great Plains eastward) seem to form two discrete evolutionary groups, and this geographic distinction is the first character used in the taxonomic key. Most western species can at least occasionally produce plants with multiple-flowered scapes, while eastern species always have a single flower. Bulbs of western species vary from ovoid to slender and elongate, while all eastern species have ovoid bulbs. Fruits of western species vary from obovoid to narrowly oblong, while all eastern species have obovoid fruits. In species with mottled leaves, the pattern of mottling in eastern species is a more or less random dappling (resembling that of the Eurasian Erythronium dens-canis), while in western species it takes the form of elongate lateral streaks or veining, often more or less symmetrical on either side of the midline. Several eastern species, but only a single western species (E. multiscapideum), propagate vegetatively by stolons originating largely from nonflowering bulbs. (The term “stolon” is used here to refer to the slender, white, elongate, underground structures found in Erythronium.) In E. propullans, one stolon per plant is produced from the flowering scape below ground level. In species with stolons, populations often contain relatively few flowering plants. In the following descriptions, measurements of bulbs and leaves refer to flowering plants.

The base chromosome number in Erythronium is x = 12, except for the white-flowered species of eastern North America, E. albidum, E. mesochoreum, and E. propullans, which have x = 11. Both diploid and tetraploid species occur with each base chromosome number (2n = 22, 24, 44, and 48).

Although the pollination biology of most species of Erythronium is not well known, that of the bumblebee-pollinated E. grandiflorum has been the subject of extensive study (e.g., J. D. Thomson and D. A. Stratton 1985; J. D. Thomson and B. A. Thomson 1989). The oligolectic bee Andrena erythronii is associated with Erythronium in northeastern North America, although A. erythronii visits other species of plants, and other insects also visit Erythronium (P. Bernhardt 1977; W. E. LaBerge 1987).

Selected References

Applegate, E. I. 1935. The genus Erythronium: A taxonomic and distributional study of the western North American species. Madroño 3: 58–113.

Mathew, B. 1992. A taxonomic and horticultural review of Erythronium L. (Liliaceae). Bot. J. Linn. Soc. 109: 453–471.

Parks, C. R. and J. W. Hardin. 1963. Yellow erythroniums of the eastern United States. Brittonia 15: 245–259.

Robertson, K. R. 1966. The genus Erythronium (Liliaceae) in Kansas. Ann. Missouri Bot. Gard. 53: 197–204.

Shevock, J. R., J. A. Bartel, and G. A. Allen. 1990. Distribution, ecology and taxonomy of Erythronium (Liliaceae) in the Sierra Nevada of California. Madroño 37: 261–273.

Lower Taxa

Erythronium albidum, Erythronium americanum, Erythronium californicum, Erythronium citrinum, Erythronium elegans, Erythronium grandiflorum, Erythronium helenae, Erythronium hendersonii, Erythronium klamathense, Erythronium mesochoreum, Erythronium montanum, Erythronium multiscapideum, Erythronium oregonum, Erythronium pluriflorum, Erythronium propullans, Erythronium purpurascens, Erythronium pusaterii, Erythronium quinaultense, Erythronium revolutum, Erythronium rostratum, Erythronium taylorii, Erythronium tuolumnense, Erythronium umbilicatum

Key

1	Plants of e North America, from the Great Plains eastward.	> 2
1	Plants of w North America, from the Rocky Mountains westward.	> 7
2	Tepals yellow.	> 3
2	Tepals white to pink or lavender.	> 5
3	Capsule apex long-beaked; style persistent, forming beak on capsule; inner tepals with conspicuous, well-developed auricles.	Erythronium rostratum
3	Capsule apex rounded, truncate, apiculate, umbilicate, or indented; style deciduous or base forming a small apiculum; auricles of inner tepals small or absent.	> 4
4	Capsule apex rounded, truncate, or apiculate, capsules held erect or at least off ground; style swollen distally or ± terete; stigma lobes erect or recurved; inner tepals with small auricles; stolons 1–3 per bulb, mostly on 1-leaved plants.	Erythronium americanum
4	Capsule apex indented, umbilicate, or rarely rounded, capsules ± resting on ground on reclining peduncles; style ± terete; stigma lobes spreading; tepals without auricles; stolons absent, or 1 per bulb of 1-leaved plants.	Erythronium umbilicatum
5	Flowering plants reproducing vegetatively by stolons produced halfway up stem; tepals 8–15 mm; se Minnesota.	Erythronium propullans
5	Flowering plants reproducing vegetatively by droppers or offshoots or by stolons arising from bulbs; tepals 15–40 mm; widespread.	> 6
6	Tepals strongly reflexed at anthesis; leaf blade mottled, ± flat; capsules held erect; usually mesic bottomlands.	Erythronium albidum
6	Tepals spreading at anthesis; leaf blade usually not mottled, conduplicate; capsules resting on ground; prairies, glades, dry, open woods.	Erythronium mesochoreum
7	Leaf blade distinctly irregularly mottled with irregular streaks of brown or white; tepals violet-pink to white or creamy white, often yellow at base but never throughout.	> 8
7	Leaf blade uniformly green (faintly mottled with brown or white in E. elegans and E. quinaultense); tepals yellow or white, sometimes pinkish in age.	> 14
8	Filaments flattened, wider than 2 mm; stigma lobes 2–6 mm.	> 9
8	Filaments linear, less than 0.8 mm wide; stigma unlobed or with lobes shorter than 4 mm.	> 10
9	Tepals white to creamy white at anthesis, sometimes pinkish in age.	Erythronium oregonum
9	Tepals uniformly clear violet-pink at anthesis.	Erythronium revolutum
10	Tepals violet to pink, dark purple at base.	Erythronium hendersonii
10	Tepals ± white with yellow base.	> 11
11	Style 5–10 mm; anthers yellow, white, or cream (sometimes pink, reddish, or brownish red in forms of E. citrinum).	> 12
11	Style 10–15 mm; anthers white to cream.	> 13
12	Anthers yellow; style often bent; tepals bright yellow at base.	Erythronium helenae
12	Anthers white to cream; style straight; tepals usually pale yellow at base.	Erythronium citrinum
13	Scape (when flowers more than 1) branched well above leaves; bulbels sessile or absent; flowering individuals generally abundant in populations.	Erythronium californicum
13	Scape (when flowers more than 1) branched near ground level; bulbels produced at ends of long slender stolons; flowering individuals generally uncommon in populations (most plants 1-leaved and vegetative).	Erythronium multiscapideum
14	Tepals yellow.	> 15
14	Tepals white to creamy white with yellow zone at base, sometimes tinged pink.	> 17
15	Style and filaments yellow; tepals 15–28 mm; stigma unlobed or with very short, rounded lobes shorter than 1 mm; inflorescences 1–10-flowered.	Erythronium pluriflorum
15	Style and filaments ± white; tepals 20–35 mm; stigma unlobed or with slender, recurved lobes (1–)2–4 mm; inflorescences 1–4-flowered.	> 16
16	Inflorescences usually 1-flowered; style 10–15 mm; stigma unlobed or with lobes (1–)2–4 mm; tepals (in live specimens) often with narrow, paler zone at base.	Erythronium grandiflorum
16	Inflorescences usually 1–4-flowered; style 8–10 mm; stigma unlobed or with lobes shorter than 1 mm; tepals uniformly yellow	Erythronium tuolumnense
17	Stigma ± unlobed, or with lobes shorter than 1 mm.	> 18
17	Stigma with slender, usually recurved lobes 1–5 mm.	> 21
18	Tepals 10–20 mm, auricles absent.	Erythronium purpurascens
18	Tepals 20–45 mm, inner auriculate.	> 19
19	Tepals less than 1/3 yellow; filaments white; leaves 6–17 cm; inflorescences 1–3-flowered; sw Oregon, nw California	Erythronium klamathense
19	Tepals 1/2–2/3 bright yellow proximally; filaments white or yellow; leaves 10–35 cm; inflorescences 1–8-flowered; Sierra Nevada of California.	> 20
20	Filaments white; anthers yellow.	Erythronium pusaterii
20	Filaments yellow; anthers cream.	Erythronium taylorii
21	Tepals white to creamy white; filaments linear, less than 0.8 mm wide.	> 22
21	Tepals tinged with pink; filaments linear to lanceolate, at least 0.8 mm wide.	> 23
22	Tepals narrowly ovate, 20–35 mm, length at least 4 times width; style 15 mm or shorter; leaf blade narrowed gradually to petiole; nw Idaho, w Montana, e Washington.	Erythronium grandiflorum
22	Tepals broadly ovate to broadly lanceolate, 25–45 mm, length (at least of the inner) less than 4 times width; style 13–25 mm; leaf blade narrowed ± abruptly to petiole; sw British Columbia, w Oregon, w Washington.	Erythronium montanum
23	Inner tepals ± white, outer ± white and often strongly marked with pink, especially abaxially and along midline; Coast Ranges, Oregon.	Erythronium elegans
23	All tepals white proximally, shading to pink at outer margins and tips; Olympic Mountains, Washington	Erythronium quinaultense