Streptanthus oblanceolatus

Streptanthus oblanceolatus is a biennial species with oblanceolate basal and cauline leaves, the cauline leaves reduced upward, whereas S. tortuosus is an annual to perennial species with oblong to widely ovate basal leaves and round to oblong cauline leaves, the upper cauline leaves often larger. S. oblanceolatus has numerous inflorescence bracts and yellow sepals, while S. tortuosus generally has just one inflorescence bract and purple sepals (though sepals are yellowish in var. flavescens). Finally, S. oblanceolatus has an entire stigma, an adaxial stamen pair that is connate below the middle with sterile anthers, and spreading, straight to slightly curved siliques, whereas S. tortuosus has a weakly lobed stigma, an adaxial stamen pair the is free to the base with fertile anthers, and generally reflexed, curved siliques (Nelson and Nelson 2009).

In fissures and soil pockets on an exposed, nearly vertical serpentine rock face above a highway and in gravels below the highway, within an open Quercus chrysolepis-Pseudotsuga menziesii forest on east to north-facing aspects. Overstory and understory cover are lacking and shrub and herb cover are sparse (<2%). Its few associates include Selaginella wallacei, Eriogonum nudum, Keckiella corymbosa, Sedum spathulatum, Pentagramma triangularis ssp. triangularis, and Polystichum imbricans ssp. imbricans. A few plants were found on a roadside mound of rockslide scrapings in association with Bromus hordeaceous, Briza maxima and Avena fatua (Nelson and Nelson 2009).