I dont think they do much growing, they bring a lot of stuff in from people who do though. often you will hear him say 'we just got a few of these in' or 'these are the fattest apples we've seen, they wont be here long etc'
my Hackberry was from about 7 he imported from spain one year. then a few months ago he had about 5 smaller ones again from spain or italy.
Chan is the biggest and most prolific grower of his own bonsai stock in this country, all air layers and ground growing. he hasnt imported a maple for years n years. that must save him tons of money.