The Japanese name for such people is sensei. There are other words that have
entered the English language from various directions, such as maven or guru,
but if you call someone a bonsai maven or a bonsai guru, people may think you
are joking.
Do you realize that the Spanish word hacienda (fazenda in Portuguese), which is
a large farm, is the equivalent of the English word factory?
(The word maven means someone who understands, from Hebrew via Yiddish.)
Iris,
Central NY, Zone 5a, Sunset Zone 40
"When you come to a fork in the road, take it." Yogi Berra