This brassica has me stumped. It was photographed in late summer in New York, growing thickly beside a stream in lawn area. Suggestions so far are that it is Barbarea verna or B. vulgaris (which I've only noticed in early spring). The flowers in late summer are perplexing - if the plants were mown, could they have regenerated and flowered again? The stalks were no more than 8cm tall. The leaves had a matt, soft texture, rather than smooth and glossy.
We may not see the cauline leaves here. If this plant was regularly cut, only the basal leaves are developed. The same is true for Barbarea vulgaris, of course. But in Barbarea, the siliques are more ascending or curved upward and they look longer compared to the pedicel, whereas in Brassica rapa the sliques are shorter than pedicels, at least when they are immature.
Thank you. An eloquent response. Another suggestion just received has been Rorippa sylvestris - which I rather like. http://www.illinoiswildflowers.info/weeds/plants/creeping_cress.htm - These suggestion are coming from a Plant Identification group on Facebook... https://www.facebook.com/groups/156706504394635/
