  The largest plant families are: Asteraceae (Sunflower family) ~24,000 species Orchidaceae (orchid family) ~20,000 species Fabaceae (Legume family) ~18,000 species … Poaceae (grass family) ~10,000 species Rubiaceae (coffee family) ~10,000 species.oover Dam is the largest hydro electric dam in the world. This Is Totally Wrong. The Largest Hydro-Electric Dam In North America Is The Mighty Grand Coulee Dam In The State O … f Washington Which Produces 3 Times The Megawatts As Hoover Dam. Grand Coulee Produces 6,809 megawatts And Hoover Dam Only 2,078 megawatts.