Flora of North America species comparison

Of conservation concern.

In the late nineteenth century, botanist and bulb merchant Carl Purdy employed Native Americans to collect bulbs of lilies and other desirable plants in the area around Eureka, California, and Lilium occidentale was among the species he was brought. After Purdy described Lilium occidentale in 1897, the plant came into great demand. He later (C. Purdy 1937) lamented that almost no plants were available for cultivation. Populations fluctuated in the middle of the twentieth century and frequently declined dramatically from overcollecting following publicity that the plants had recovered and flowered. Much habitat was subsequently lost to ecological succession and land conversion. Fortunately, several large populations have recently been discovered near Crescent City, California, and completion of a recovery plan (Fish and Wildlife Service 1998) bodes well for the future of this state and federally protected plant.

Lilium occidentale occurs in scattered populations from Humboldt Bay, California, to Coos Bay, Oregon, always within six kilometers of the ocean. Plants near Humboldt Bay occur in coastal prairies and scrub, whereas many Oregon populations are found in sphagnum bogs. Typical Oregon and extreme northern California plants in the vicinity of Crescent City (Del Norte County) have an irregular bulb that occasionally is nearly erect (0.3–0.7 times taller than long versus 0.3–0.5 in Humboldt Bay plants). In northern plants the leaves are often scattered—though they are whorled in larger plants—and extremely long and thin [4.2–26.3 × 0.4–2.7 cm (4.6–28.6 times longer than wide) versus blade 4.1–18.9 × 0.7–3 cm (4–17.4 times longer than wide)] in Humboldt Bay plants. Flowers of Oregon plants are marginally smaller, have somewhat narrower sepals (4.4–7.6 × 0.8–1.5 cm) than Humboldt Bay plants (4.4–8.1 × 1–1.8 cm), and typically appear somewhat later. These differences have provoked discussion about the merits of subdividing this species, but many of the differences appear to be related to habitat rather than genotype. For example, plants from Shores Acres State Park in Coos County, Oregon, occur in a coastal bluff setting that is similar to habitats near Humboldt Bay, and these lilies share many of the same vegetative and floral characteristics of Humboldt Bay plants. Subspecific differentiation appears to be unwarranted.

Lilium occidentale is distinguished from similar species such as L. pardalinum by the closely parallel stamens and adaxial green star formed by the conspicuously green sepal and petal bases, a characteristic also discernible in the abaxial surface of the buds. This green star is present in nearly all flowers when first opened, but changes to yellow or yellow-orange as the flowers age. The green star of certain eastern taxa (e.g., L. superbum) is also diagnostic for them but is primarily formed by glossy green adaxial nectaries and is not so prominent in bud.

Frequent hybrids with Lilium columbianum in Oregon occur primarily where human disturbance has introduced that species into boggy areas via drier open pathways such as powerline right of ways and roads.

With the likely exception of Lilium canadense, L. occidentale is the only North American pendent lily that is pollinated almost exclusively by hummingbirds (in California primarily the Allen’s hummingbird [Selasphorus sassin (Lesson), family Trochilidae]). Its pendent red flower is transitional between butterfly-pollinated forms like L. pardalinum and the classical bird-adapted flowers of L. maritimum and L. bolanderi that are more tubular and horizontal.

The Karok ate Lilium occidentale bulbs after baking them in an earth oven (D. E. Moerman 1986).

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

B. Boivin and W. J. Cody (1956) proposed uniting Lilium michiganense and L. superbum as subspecies of L. canadense on the basis of overall similarity, though it is now well accepted that L. superbum does not belong there. There can be little doubt as to the close relationship between L. michiganense and L. canadense, however, and vegetatively the two are often indistinguishable. Hybrid intermediates occur across a wide band where the distributions meet in central Ohio and northwestern New York (R. M. Adams and W. J. Dress 1982). It would not be unreasonable to include L. grayi and treat them as subspecies, but floral differences among the three are comparable to those between other species in the genus.

Farwell’s proposed varieties uniflorum and umbelliferum were described from young plants with single flowers and umbellate inflorescences respectively, but young plants with these characteristics are found throughout the range of this species.

Plants examined from east-central Tennessee (e.g., Wayne and Coffee counties) that were previously referred to Lilium michiganense are L. superbum in some cases, in others L. canadense perhaps introgressed with L. michiganense.

The Michigan lily often co-occurs in tallgrass prairies with Lilium philadelphicum; here as everywhere it usually blooms much later. However, it flowers earlier than L. canadense where their ranges are contiguous in Ohio (E. L. Braun 1967).

Lilium michiganense is pollinated primarily by swallowtail butterflies; in the southern part of its range these include the pipevine [Battus philenor (Linnaeus), family Papilionidae]. Great spangled fritillaries [Speyeria cybele (Fabricius), family Nymphalidae] also visit this species and carry its pollen, though it is unlikely that this brushfooted butterfly is a major pollinator.

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