Not according to this http://www.telegraph.co.uk/history/world-war-one/10218932/Your-Country-Needs-You-The-myth-about-the-First-World-War-poster-that-never-existed.html
Indeed, surely a poppy would suffice.
I tried to use one of those at the Dartford toll boths and the woman got irate! They called security over in the end!