In 1957 rosettes apparently of Rorippa sylvestris appeared in a clear area in my garden. These did not flower but spread rapidly from the original small colony of a few plants during the season of 1957. Wishing to learn more concerning these plants and to identify the species with more certainty, I allowed them to remain to observe their flowers. The small colony of a few plants had spread very rapidly in 1958, forming a large dense colony of rampant matted, more or less spreading or ascending stems, which showed tiny buds and unopened flowers in profusion. The colony now covered an area near 25 to 30 square feet in area. The flowers appeared to be abortive, remained closed and produced no normal blossoms, siliques or seed at any time.