Cakile edentula (Bigelow) Hook.
American sea rocket, named for its rocket-like seed pods, is native to beaches and sand dunes of eastern North America. It is an invasive in Japan and Australia.
Plants: Plants are 6-20" (15-50 cm) high, and about the same around, with succulent stems. They look rather disheveled, like tumbleweed.
Flowers: Upper stems bear racemes of flowers 2-10" (5-25 cm) long. Flowers are up to ¼" (6.3 mm) around, lavender to white, with 4 petals, 6 stamens, and a pistil with a single style. Flowers appear from July to September.
Fruits: Each seedpod is elongated, ½-¾" (1.3-1.9 cm) long, and comprised of two segments. The lower segment is roughly cylindrical and about ¼" (6.3 mm) long. The upper segment is a cylinder about ½" (1.3 cm) long, that tapers to a beak. Each segment typically contains a seed. There is a reason for the complex-seeming design: the upper segment floats, and carries its payload on a sea adventure to a distant locale. Meanwhile, the lower segment typically sprouts nearby.
Edibility: Young stems and leaves are “pungent,” somewhat like horseradish. Young leaves are mixed with other greens in salads, and older stronger tasting leaves are cooked with other leaves as a potherb.
Cakile edentula var. lacustris at Illinois Wildflowers
Cakile edentula on the New England Wildflower Society’s GoBotany site
Cakile edentula at the Lady Bird Johnson Wildflower Center
Cakile edentula on JSTOR Plant Science
Cakile edentula description by Thomas H. Kent, last updated 3 Jul 2017.