St. Patrick is said to have used the shamrock in explaining to the pagan Irish the idea of the Holy Trinity. |access-date= requires |url= (help) ↑ Nelson (1991), p. 14 Harvp 1 Nelson 2 1991 Page 14 ↑ Website (Naturegate) showing images of young leaves of lesser trefoil ↑ Gerard's Herbal 1597 online 1 2 "NS07 Threlkeld Shamrock | a whole new world". dublincitypubliclibraries.com.