She had been RHS director of gardens and estates since May 2006.
Jim Gardiner will be new director of horticulture and will continue his role as chief curator of the society.
Cherry is a trained horticulturist and landscape architect with 28 years experience.
She started as a greenhouse grower and later worked in management and development of public gardens, in Canada.
Cherry was garden director at the City of Vancouver's VanDusen Botanical Garden after working at that City's parks and recreation department. She was superintendent of the Allan Gardens conservatory, and then of all floral production and then City Arborist. She also completed a degree programme in Environmental Studies at the University of Toronto before moving to VanDusen Botanical Garden in 2000.
Head-hunters from the RHS used a series of video conference interviews to recruit Cherry in 2006.
Gardiner will have overall responsibility for the policy and management of horticultural standards, oversee the RHS plant committees and the society's plant trials programme, and fulfil an ambassadorial role for the organisation.