This little plant was growing beside a rough path. Sometimes the Vervain (Verbena officinalis) is grown in gardens but it is really a wild flower which grows on bare ground or rough grassland reaching a height of up to 70 cms.   According to Richard Mabey in “Flora Botanica”  
It was once a venerated plant, valued not just as a panacea (it was trumpeted as a cure for the plague in the Middle Ages) but as a magical charm, which could both protect against witches and demons and conjure up devilry of its own. It was traditionally associated with the gods of war, and gunflints were sometimes boiled with rue and vervain to make them more effective.  …….    The Isle of Man is the last British redoubt of belief in vervain’s potency …….   Mere possession of it conferred all manner of protection.  A person going on a journey would carry a piece and many a Manxman would have a piece permanently sewn into his clothing……..  The procedure for getting a plant is rather complicated.  It cannot be asked for directly.  Broad hints will be dropped and the possessor will take the hint and a plant will discreetly change hands, usually wrapped in paper.  No word should be exchanged.  It must always change hands from man to woman or vice-versa.