Sorry! That's the wrong answer. This weed is St. John's-Wort, which occurs throughout Ontario in pastures, edges of woodlots, roadsides, abandoned fields, water areas and occasionally in lawns and lower borders.

If eaten by horses, St. John's-Wort may cause photosensitization, since this weed contains black dots composed by hypercin, a pigment that is absorbed by the body and activated by exposure to sunlight. Ingestion can result in a condition in which patches of white or light-coloured skin become seriously sunburned under normal exposure to sunlight.