Dodecatheon dentatum, the only consistently white-flowered shooting star in our flora. Illustration by Jeanne R. Janish from Hitchcock et al. 1969, Vascular Plants of the Pacific Northwest, courtesy of University of Washington Press.

     In his Synoptical Flora of North America, published in 1878, the Harvard botanist Asa Gray—a pre-eminent figure among 19th century American taxonomists—treated the Shooting Star genus Dodecatheon (Family Primulaceae) as comprising a single species D. meadia, divided into seven varieties.  Only a decade later, Edward L. Greene, a professor at the University of California, commented that Gray had “a mere herbarium acquaintance with the plants,” whereas “knowledge of the plants...in the living state, either on their native soil or in gardens” was necessary to “diagnose the species.”

     Confident of his abilities as a field naturalist and collector of western American plants, Greene began in 1888 to divide Dodecatheon into numerous separate species.  Over several decades he described 18 species and varieties in the western United States, while other botanists of the early 1900s, including C. V. Piper, Alice Eastwood, P. A. Rydberg, Thomas Howell, and Aven Nelson also “diagnosed” many additional new species of the genus.  Apparently, in the eyes of Asa Gray, all shooting star plants looked pretty much alike, while to botanists who knew Dodecatheon in its native haunts, numerous differences could be found, if one looked closely enough.

     In general terms, it would seem that Gray’s interpretation of the genus, which is confined to North America and adjacent Siberia, as a single, highly variable species was understandable.  The flowers of shooting stars have a distinctive, easily recognized pattern, and the supposed species differences are merely minor variations on a single floral theme.  The pendant flowers with upraised reddish-purple petals and projecting cone-shaped anthers are adapted to pollination by bees, which gather pollen by grabbing the petals and vibrating the flowers with a buzzing of their wings.  Similar “buzz-pollinated” flowers are found in genera of the potato family, such as Solanum and Lycopersicon, and perhaps in the liliaceous genus Erythronium.  No species of Dodecatheon diverge from this pollination system, so their flowers must inevitably maintain the same architectural bauplan.

     In the Oregon Vascular Plant Checklist we recognize nine species of Dodecatheon, with two additional subspecies under one species, D. pulchellum.  This comes close to the eight species and three additional varieties mentioned in Flora of the Pacific Northwest.  One Oregon species, found in the northwest coastal counties and adjacent Washington, has yet to be formally described.  A complete treatment of the genus, published by H. J. Thompson in 1953, was relatively conservative in recognizing 14 species and 13 additional subspecies in North America.  This is a long way from the single species envisioned by Asa Gray, but it is fewer than the large number named by Greene and his contemporaries early in the present century.

     Shooting stars show their greatest diversity in the Pacific Coast states, occupying a wide range of environments—from arctic and alpine tundra to mountain meadows, wet cliffs and rocky riverbanks, serpentine seeps, oak woods, moist prairies, summer-dry grasslands, and sagebrush deserts.  Lacking floral differences, the species have evolved ecological and geographical barriers to intercrossing.  Additionally, polyploid differences in chromosome numbers may prevent hybridization, even between plants within the same morphologically defined species.

     The “little things that make a difference” in Dodecatheon taxonomy include minor variations in stigmas, anthers, capsules, petal numbers, leaf shape, and pubescence.  The key to species in Flora of the Pacific Northwest, pages 352-353, illustrates these traits quite well.  I found that the stigma, anther, and pubescence features are well preserved in herbarium specimens; mature capsules, however, are seldom collected.  In only a few species is leaf shape consistent enough to be useful.  White-flowered forms occur in several species, but only in D. dentatum is this trait consistent.  Similarly, 4-petalled flowers are uniformly present only in D. alpinum but are sporadic in some other species.  A list of the Oregon taxa, with some of their important features and their geographic range in the state, is given below:

Dodecatheon alpinum:  Style with an enlarged “pin-head” stigma; petals and anthers four; filaments free;  tissue between the anther sacs (“connective”) transversely wrinkled; plants glabrous; mountain stream-banks and meadows [closely allied with D. jeffreyi].

Dodecatheon jeffreyi:  Style with an enlarged “pin-head” stigma; petals and anthers usually 5, rarely 4;  filaments free; anther connective transversely wrinkled; plants glabrous or more often lightly  glandular-pubescent, especially the inflorescence; mountain streambanks, marshes and meadows  [plants often larger than D. alpinum].

Dodecatheon cusickii:  Stigma not enlarged; filaments united basally into a yellow tube 1.5-2.5 mm long; anther connective smooth; whole plant densely glandular-pubescent; grasslands and sagebrush  lands east of the Cascade Mtns. [closely allied with D. pulchellum].

Dodecatheon poeticum:  Stigma not enlarged; filaments united basally into a purplish tube 1.5-2.0 mm long; anther connective smooth or transversely wrinkled; whole plant densely glandular-pubescent; oak woods, grasslands, and basalt outcrops, Columbia River Gorge [closely allied with C. cusickii].

Dodecatheon hendersonii:  Stigma not enlarged; filaments united basally into a purplish tube 2-4 mm long; anther connective smooth or transversely wrinkled; leaves round to broadly obovate, smooth-margined, glabrous; prairies and oak woods west of the Cascade Mtns.

Dodecatheon pulchellum:  Stigma not enlarged; filaments usually united into a tube; leaves entire, usually glabrous; anther connective smooth.  ssp. pulchellum:  filament tube yellow; anthers 3.5-5.0 mm  long; widespread east of the Cascade Mtns., from sagebrush lands to high alpine.  ssp.  macrocarpum:  filament tube yellow; anthers 5.5-7.0 mm long; Columbia Gorge, Willamette Valley and adjacent foothills.  ssp. monanthum:  filament tube purplish; anthers 3.5-5.5 mm long; scattered sites east of the Cascade Mtns., Willamette Valley, and Siskiyou Mtns.

Dodecatheon conjugens:  Stigma not enlarged; filaments free; anther connective strongly transversely wrinkled; leaves glabrous or lightly pubescent, often obovate, smooth margined; sagebrush lands to mountain meadows east of the Cascade Mtns.

Dodecatheon dentatum:  Stigma not enlarged; petals white; filaments free; anther connective smooth; leaf  blades glabrous, ovate, often with toothed margins; wet cliffs, often near waterfalls, Columbia River Gorge.

Dodecatheon species novum:  Stigma not enlarged; petals reddish-purple; filaments free; anther connective smooth; leaf blades glabrous, oblanceolate, often with toothed margins; North Coast Range, on rocky peaks and bare basalt riverbanks, possibly also in the Siskiyou Mtns.