Yellow Rocket (Barbarea vulgaris) photo = Rocket,Yellow_MAC_©DaveSpier_D029567iN_5D
Winter Cress, a.k.a. yellow rocket (Barbarea vulgaris); I was actually photographing the goslings at the edge of Red House Lake, but it's pretty easy to see the yellow mustard; photo ref.: Rocket,Yellow_ANP_©DaveSpier_D006772e
Full sun. Soil is fairly dry at surface due to baking from the sun. Vegetation is patchy in this area and does not cover 100% of the surface. About 2' tall. Next to a newly restored wetland. Keyed out with Newcomb's Wildflower Guide.
Though they have similar flowers, the leaves of this mustard are very different from the one posted earlier:
Barbarea (winter cress or yellow rocket) is a genus of about 22 species of flowering plants in the family Brassicaceae, native to temperate regions of the Northern Hemisphere, with the highest species diversity in southern Europe and southwest Asia. They are small herbaceous biennial or perennial plants with dark green, deeply lobed leaves and yellow flowers with four petals.