Bensley was Hillier Garden Centres' hardy plant buyer having started at the business in 1987. She was also editor of the Hillier Gardening Club Magazine.
She is also a National Association of Flower Arranging Societies (NAFAS) judge and gold medal winner at Chelsea for floral art.
She said: "I'm off to start my own floristry business but also dabbling still in the horticultural world via various projects."
Hillier is seeking a replacement through MorePeople.