Shamrock, a popular name for several clover plants having leaves divided into three small leaflets. The shamrock is a national emblem of Ireland, worn especially on St. Patrick's Day. According to legend, Saint Patrick used the three-sectioned leaf to illustrate the doctrine of the Trinity.
The suckling clover ( Trifolium dubium)is widely regarded as the true shamrock; however, white-clover ( T. repens)and the hop clover ( Medicagolupulina)are also used as shamrocks. All are of the pea family, Leguminosae.The shamrock is a three-leaf clover.