Fleabane ?
This yellow member of the daisy family grows on wet ground and is flowering now. Its common name suggests it would get rid of fleas, but its specific name Pulicaria dysenterica suggests a cure for dysentery(and fleas are in a superfamily called Pulicoidea). A web search found “The bruised leaves have a soap-like smell. They are astringent and can be used in the treatment of dysentery.” However, “Flora Britannica” says “its insect-deterrent powers may not be entirely fanciful. It is a comparatively close relative of the species which supplies the insecticide ‘pyrethrum’.”

