Clover over here tends to have oval shaped leaves. The only ones I have seen here growing wild with heartshaped leaves are the little ones with yellow flowers.

I was happy to know that they are one of the one that have been dubbed "Shamrock"

One of the sites I looked at also said that Shamrock comes from "Shamroy" (not the Irish spelling, obviously), meaning "clover".

Dunno how true that is, however...