Four fire engines and around 25 firefighters were called to a shed fire on High Road in East Finchley.
Most of a range of single-storey sheds in an allotment were damaged by fire. There were no reports of any injuries.
Station Officer Mark Smith, who was at the scene, said: “Firefighters arrived to find the fire in an allotment quite far back from the entrance gate. A large, prefabricated shed was alight and the fire had spread to another nearby shed.
“Crews faced poor visibility as they worked to search the premises and bring the fire under control.”
The incident was also the first night shift of Finchley Fire Station’s new trainee firefighter, Marina Busca. She said: “My first night shift went really well. We made sure that the fire had not spread to any further areas of the allotment and worked together to make the scene safe.”
The Brigade was called at 0257 and the fire was under control by 0448. Fire crews from Finchley and Hornsey fire stations attended the scene.
The cause of the fire is under investigation.