When more than $20,000 worth of bonsai were stolen from Fukujyuen, a shop selling the carefully cultivated mini trees in Gunma Prefecture, Shuichi Baba felt anger but also deep sadness for the miniature trees he had lost.

"I even blamed myself,” Baba said of the disappearance of more than a dozen junipers and other plants he had nurtured for as long as two decades. "Why couldn’t I have woken up in the middle of the night to stop it?”

Baba isn’t the only one to see his living creations purloined in the dark. There were about 30 cases of such theft last year, according to the Nippon Bonsai Growers Cooperative.