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Oil neststraw
Stylocline citroleum

Status

None federal or state. California Native Plant Society List 1B.

Life History

Oil neststraw, an annual, flowers in April and reproduces strictly by self-pollination. The extant occurrences and several of the historical localities are in petroleum-producing areas, giving rise to both the common and scientific names. This species grows on flats and on slopes in saltbush (Atriplex spp.) or mesquite (Prosopis glandulosa var. torreyana) scrub, often in sparsely-vegetated areas that have a well-developed cryptogamic crust. Plant species associated with oil neststraw include everlasting neststraw (Stylocline gnaphaloides), California filago (Filago californica), Hoover's woolly-star (Eriastrum hooveri) [CL], many-flowered eriastrum (E. pluriforum), red brome (Bromus madritensis ssp. rubens), common saltbush (Atriplex polycarpa), and white burrobush (Hymenoclea salsola). Oil neststraw has been found at elevations of 60 to 320 m on both sandy and clay soils.

Oil neststraw is believed to have originated as a hybrid of two common species, everlasting neststraw and California filago. However, oil neststraw satisfies the definition of a species because it is capable of reproducing itself without further crossing of the parental species. Oil neststraw is inconspicuous because it grows low to the ground and does not have showy flowers. It has trailing, woolly stems and small, woolly leaves. Each round flower head contains many individual florets, which consist of reproductive parts and papery scales covered with woolly hairs. The fruits are tiny, brown achenes.

Distribution

Five populations of oil neststraw were known historically, based on collections made from 1883 to 1935. Four of the occurrences were in Kern County, in the vicinities of Bakersfield, McKittrick, and Taft. The fifth collection was made in San Diego County. The location descriptions are too vague to determine whether oil neststraw remains at historical sites. Urban development has almost certainly eliminated the historical populations of oil neststraw in the vicinities of San Diego and Bakersfield. Known occurrences are confined to the Elk Hills Naval Petroleum Reserve and the adjacent Coles Levee Ecosystem Preserve in Kern County, where they were discovered in recent years.

Classification

Subclass ASTERIDAE, Order ASTERALES, Family ASTERACEAE, Genus Stylocline, Species citroleum

Subspecies

None.

Recent Synonyms

None.

Other Common Names

None.

References

Morefield, J.D. 1992. Three new species of Stylocline (Asteraceae: Inuleae) from California and the Mojave Desert. MadroZo 39:114-130; Morefield, J.D. 1993. Stylocline. Pp. 348-349 in The Jepson manual: higher plants of California (J.C. Hickman, ed.). University of California Press, Berkeley, 1400 pp.; Skinner, M.W., and B.M. Pavlik, eds. 1994. Inventory of rare and endangered vascular plants of California. Fifth edition. Spec. Publ. No. 1, California Native Plant Society, Sacramento, 338 pp.; Rarefind, California Natural Diversity Data Base, Sacramento.

Size

Stem length:
< 13 cm Flower head:
< 5 mm in diameter
Floret:
1.2-2.1 mm long Fruit:
0.8-1 mm long

Identification

Oil neststraw is difficult to distinguish from closely related species because the identifying characters are microscopic. Key characters include scale size and shape, number of bristles on the achene, and degree of woolliness.

Authors of Profile

E.A. Cypher

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