The chapel, which is known as the New Room, is located in a busy 1960s shopping area in Bristol and currently has a cobbled courtyard.
The firm was approached after a public exhibition of the contemporary street design proposed by Reckless Orchard for the street outside the chapel.
Reckless Orchard director Les Baker explained that the intention is to create a "flexible space" that can be used by visitors to the New Room as well as passers-by, local workers and tourists.
Espaliered fruit trees and herbs will reflect Wesley's interest in healthy living, while climbing plants and trees will help soften the enclosing walls and screen unattractive rear views of the shopping arcades.
The overall objective is to create a calm, reflective, green space with subtle Georgian themes. The project is due to start on site in the New Year and should be completed by next summer.
An appeal has been set up to help raise funds for the project. See www.newroombristol.org.uk.