Officers from the Met Police have discovered more than 150 plants some which managed to grow 5ft high.
The discovery was made in an area of land in Kingston which is the size of a football pitch.
A member of the public reported the site to police.
Responding officers described the site on Lower Marsh Lane, Kingston as a forest of small christmas tress, centered around a gazebo.
The site has been well planned, the offender(s) would have had to walk 20 mins on foot to access the remote site.