Banning was motivated from an early age to investigate the workings and beauty of the natural world, which led her to specialize in mycology. She collected mushrooms and other fungi throughout Maryland, put together a scientific library, set up a private herbarium, and kept an illustrated record of all she found. In fact, between 1868 and 1888, Banning created a remarkable and significant book of watercolor illustrations of mushrooms (including some species new to science), faithfully documenting the details of their physical appearance both in pictures and in words.

Her devotion to science is even more astounding considering the obstacles placed before her. She was essentially a practicing scientist without the support of a major institution. Her private letters reveal her frustration in being excluded by the nineteenth century scientific establishment, which was not eager to accept a woman into its fold. As she worked, Banning incurred increasing  financial problems caring for invalid relatives and near the end of her life was living in near poverty. 

Banning's scientific achievements remained unrecognized in her lifetime. After nearly one hundred years of obscurity, her book of water color illustrations was recently taken off the shelf and its contents brought to life again in an exhibition organized by the New York State Museum. Through this exhibition, titled "Each a Glory Bright: Mary Banning's Mushrooms," a new generation can appreciate both the scientific and artistic value of Miss Banning's work. Efforts are currently underway to exhibit this show nationally and to publish a catalog of the illustrations.

In her honor there is now a bright, orange-red fungus, which bears the name Hypomyces banningii.