Firefighters from 14 fire engines tackled the blaze, which took several hours to extinguish.
The Gardens Group managing director Mike Burks said the source of the fire, which caused several hundred thousand pounds of damage, was still being established. The glasshouse and the main building will have to be replaced.
Despite the extensive damage, staff were able to clear up and re-open just 36 hours later. Burks said: "Our suppliers have been really supportive and we've had calls from customers offering help."
He praised the efforts of staff and suppliers. G7 was able to quickly get the till system operating, while support from Solus, Haxnicks, Thompson & Morgan and Suttons "had been extraordinary".