Contra Costa goldfields

Lastenia conjugens is an herb whose stems are simple or freely branched and erect, attaining a height of less than 40 centimeters. Their glabrous leaves, of length of approximately eight centimeters, are entire to pinnately lobed. Inflorescences appear in the form of solitary heads, with twelve to eighteen phyllaries fused at one third to less than mid length, a distinguishing hallmark for identification of this species. An involucre structure measures six to ten millimeters and may be somewhat hemispheric. The receptacle presents as dome-shaped or obconic. The yellow ray flowers may number six to thirteen petals, and the five to ten millimeter ligules are yellow as well. The yellow disk flowers are numerous, and anther tips are linear to somewhat ovate. Style tips are triangular. The corollae are typically five-lobed. Style tips may be triangular or round, but typically hair-tufted. The glabrous club-shaped fruits are less than 1.5 millimeters across, black or gray in color, absent a pappus structure. The species is cross-pollinated. According to Greene, the chromosome characteristic is: 2n=12.

Lasthenia conjugens relies upon insect pollination for fertilization, and dispersal of seed is largely by gravity. In undisturbed habitats, this and other species of Lasthenia are pollinated by specialist bee species, primarily in the genus Andrena. Studies in Solano County natural and restoration habitats have shown variability between visitation rates to the two types of colonies; however, plant propagation rates were found to be similar between natural colonies and introduced ones, implying pollination is not a limiting factor of propagation. An alternative conclusion is that members of one particular insect family, Sciaridae, are also efficient pollinators of L. conjugens, since it was the only insect family to visit the restoration colonies in significant numbers (the specialist bees are absent from these areas).