Harold “Hal” Sasaki’s hands move with swift precision as he winds a length of copper wire around a tiny dwarf jade tree’s trunk. The 82-year-old’s measured gestures reflect decades of pursuing perfection in the ancient discipline of bonsai, in which artists spend years training trees into miniature facsimiles of their natural, full-grown selves. The feeling of satisfaction the practice instills hooked Sasaki when he was 18 and still living in Kona, Hawaii, his birthplace. “There’s a communication between you and the tree,” he says. “It smiles back at you.” Sasaki began teaching classes at the Denver Botanic Gardens in 1977 after moving to Colorado. Decades later, he’s seeing an uptick in interest: The Botanic Gardens has increased its usual two bonsai classes to three in recent years as more urbanites are seeking ways to commune with nature. This year, it’s offering four 12-person courses ($105), which Sasaki co-teaches, including one on April 27. The octogenarian also holds more exclusive, six-person workshops in his backyard nursery in Wheat Ridge ($150 per person; for dates, visit coloradobonsai.com). Students learn both from and with Sasaki, who, like a true artist, says he’s still pushing the boundaries of his craft—growing alongside his trees.