The wooden design in Dorset links the garden centre's fruit farm, garden centre and farm shop at West Holme Farm in Wareham.
Owner Simon Goldsack said: "Our customers asked us for many years to have a tea room, and we wanted a high-quality design with the environment in mind."
The Orchard Tea Room has a gable end for solar gain and an air-source heat pump, which is three times more energy-efficient than a traditional heating system.
It has 70 covers inside, seats 70 customers outside and overlooks a wildlife pond. An orchard is being planted next to the tea room. Goldsack commissioned Exeter-based Custom Timber Build to create an "aesthetically pleasing" building.