The development will double the size of the Perth business that Patricia and Peter Cox founded in 1973. The garden centre is now in the hands of their son, Kenneth, and his wife, Jane.
The new facility - triple-insulated and warmed with heat pumps - was designed and built by local firms Algo and shopfitter Robert Workman.
The new shop includes an all-weather plant area, a furniture shop, a houseplant section, gift, men's and women's departments, a birdcare section and a children's area.
The new greenhouse will allow customers to look and buy plants throughout the year and protect plants from winter damage.
Jane Cox said that she hoped children would particularly enjoy the new children's area, which features a Tardis and even a Dalek.
Scottish green energy heat pump installers Environmental Heating Solutions supplied "state of the air" green technology air-heat pumps. These are designed to save up to 60 per cent on a typical heating bill and can also provide cooling in summer.