Little is known of Mary Stanwell as a naturalist. She was the youngest of the four children of William Stanwell, a collector of customs, and was born in Boston, Lincolnshire. When she was a very small child the family moved to Bridge street, Gainsborough, where Mary lived, unmarried, for the rest of her life. Her main achievement in botany seems to have been the bronze medal (second place) that she was awarded for a collection of Lincolnshire plants in the Royal Horticultural Society's 1864 botanical competition. Her elder brother, Rev Charles Stanwell, was a Cambridge graduate and a fellow of St John's College (1862 - 1872) and it may be this connection which stimulated her to enter the competition - Prof Charles C. Babington was a prominent member of the college and one of its early objectors.
There are various references to Mary's herbarium and it seems that Lees, F. A., may have been familiar with its contents (Gibbons, E. J., 1975. The Flora of Lincolnshire, Lincoln), although it is not yet clear whether it was any more extensive than the 1864 competition entry.