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Phacelia inconspicua E. L. Greene

Obscure phacelia; Obscure scorpion plant

Hydrophyllaceae (Waterleaf family)

General Description: An upright, branching, annual herb with clearly spreading hairs, but not glandular, and up to 20 cm tall. There are two types of hairs on the stems and in the inflorescence: numerous fine, short, loosely curled hairs; and a fewer number of longer, stiffer spreading hairs. The leaves are entire, more or less elliptic, 1-4 cm long and about 1 cm broad, green above and somewhat paler on the underside. Lower leaves have a short, winged petiole, while the upper leaves are sessile. Inflorescences are terminal at the stem tips and consist of small coils of small, pale bluish to whitish, bractless flowers. The five petals are fused about half their length into a bell-shaped tube 3-4 mm long. Calyx segments are linear or nearly so. Stamens are equal to or slightly exserted from the corolla. The fruit is an egg-shaped capsule about 3 mm long and has 2 seeds.

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Illustration.

Field Identification Tips: Obscure phacelia is recognized by its small, branching, annual habit, spreading, non-glandular pubescence, entire (no teeth or lobes) leaves, and bractless, coiled (unfurling like the tail of a scorpion) inflorescence of small pale bluish or whitish flowers.

Phenology: Late May through June, with prime flowering conditions during early June most years.

Similar Species: In Idaho, obscure phacelia is most likely to be confused with Phacelia incana (hoary phacelia) and P. minutissima (small phacelia). These two small, annual congenerics are similar to obscure phacelia in growth form and leaf shape, but both differ in having glandular hairs and more than four seeds per fruit. Phacelia glandulifera (sticky phacelia) can co-occur with obscure phacelia, but is readily distinguished by its deeply lobed leaves and glandular herbage. Obscure phacelia usually occurs mixed with other vernal annuals. As these annuals mature and dry it can be difficult to see obscure phacelia and to distinguish it from annual Cryptantha species (e.g., C. torreyana). The pubescence of obscure phacelia is much softer compared to that of associated Cryptantha species, however.

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Habitat: In general, sites supporting obscure phacelia are fairly steep, north- to east-facing, lower- to mid-slopes lying below the rimrock of butte tops or foothill ridgetops. Snowdrifts form on these concave lee-slopes and persist late into the spring. Plants are also occasionally observed on toe-slopes immediately above ephemerally moist drainages, but never on rimrock, ridgetops, or adjacent flats. Obscure phacelia typically grows in small gaps or clearings within shrubby vegetation, on scarified or loose loamy soil lacking significant perennial vegetation and surface litter. It is often associated with game trails, old cattle trails, and gopher diggings. Microsites most often occur within Prunus virginiana dominated communities having Leymus cinereus, Symphoricarpos oreophilus, and Bromus tectorum in the understory. It is also known from Artemisia tridentata ssp. vaseyana/Pseudoroegneria spicata, and the edges of Populus tremuloides/Symphoricarpos oreophilus communities. Known Idaho populations occur between about 5,300 and 6,200 feet elevation. All Idaho populations occur on volcanic substrates, but in Nevada populations are found on limestone rock.

Global Distribution: Obscure phacelia is known from two separated areas, one a small portion of the Humboldt Mountains in northwestern Nevada, the other, a limited segment of the Upper Snake River Plain in and around the Craters of the Moon country in south-central Idaho.

Idaho Distribution: Known Idaho populations lie in a triangular area stretching from the Pioneer Mountain foothills north of Craters of the Moon National Monument, southeast for approximately 40 miles to Split Top Butte, and 30 miles east to Big Southern Butte. All populations are in western Butte and adjacent Blaine counties.

References:

Holland, R. F. 1996. Current knowledge and conservation status of Phacelia inconspicua E. Greene (Hydrophyllaceae), the obscure scorpion plant, in Nevada. Unpublished status report prepared for the Nevada Natural Heritage Program, Carson City, NV, and U.S. Fish and Wildlife Service, Reno, NV. 30 pp. plus appendices.

Moseley, R. K. 1989. Report on the conservation status of Phacelia inconspicua in Idaho. Idaho Department of Fish and Game, Conservation Data Center, Boise, ID. 20 pp. plus appendices.

Murphy, C. 2002. The conservation status of Phacelia inconspicua (obscure scorpion plant) in Idaho: an update. Idaho Department of Fish and Game, Conservation Data Center, Boise, ID. 20 pp. plus appendices.