Blanch came to San Francisco from Texas. She attended the School of Design in San Francisco, and was a classmate and became a life-long friend of Mary DeNeal Morgan.

As members of the Pacific Coast Women's Press Association, the two women made their first trip to the Monterey Peninsula. Blanch loved the place, and decided to make it home. She was curator of the Del Montey Hotel Art Gallery, specializing in local artists, many of whom moved to the Monterey area after the earthquake of 1906. In fact, in the years following the '06 quake, Josephine's Blanch's gallery was the most important gallery in northern California. Apart from her gallery and painting duties, Blanch wrote for the Del Monty Weekly and a history of art on the Monterey Peninsula entitled Barbizon Revisited. She is known for her portraits, still lifes, and landscapes. She once restored an old adobe, and sold it to John Steinbeck. Blanch never married, and passed away in November of 1951 at the age of 87.