Going through the back archives,

Going through the back archives, there was a December 10, 2000 article in London’s Sunday Express about a company called Living Props. Living Props provides beautiful gardens and forests you see in the movies today. Apparently, they will be doing the various plants in the Harry Potter movie:

He will reveal that they are doing the plants for the Harry Potter movie, but won’t budge an inch when asked about whether they will use plant doubles or totally fabricate the Whomping Willow or baby Mandrakes. It would be easier getting blood out of a stone, although knowing Brian, it would probably be polystyrene.

You can read a different article about Living Props.