Gjertson has gained a considerable reputation for his elegant floral still lifes, which follow in the tradition of Fantin-Latour. He also paints plein air landscapes that share an affinity to those of the Russian artist, Ivan Shishkin. Most of his current work is figurative, either intimate genre paintings of his family and friends or more complicated works with biblical themes or symbolic treatments of contemporary issues.
He was an exceptional member of the American Portrait Society and accepts occasional portrait commissions. His work combines a subtle naturalism with superb drawing and balanced design. He has won several awards, including three grants from the Elizabeth T. Greenshields Memorial Foundation in Montreal, Canada and the Most Popular Visitor’s Award from Sacred Arts VII at the Billy Graham Art Center in Wheaton, IL.