Justfolk's photos with the keyword: 19613-389-1b

I think this is Barbarea vulgaris, named (Mr Wikipedia tells me) for Saint Barbara, the patron saint of soldiers. Wounded, the soldiers would press this plant as balm to their wounds. It's a European plant that, like my forebears, came here and found a good home. So it grows in roadside ditches and other disturbed soil. And now, in the last days of springtide, it bursts with blooms.