The elusive artist usually confirms his work on his website and social media, and on Monday he posted images of the artwork on Instagram with no caption.
In his post, the starkly bare tree can also be seen with a plain white wall behind it – prior to creation of the mural.
Alex Georgiou, whose company owns the building with the mural on, said he found out about it late on Sunday night, and came down to see it for the first time the morning after.
He said the building was currently vacant and on the rental market.
“The question is, what do I do with it now? What am I meant to do with it now? I definitely plan on keeping it on there and letting people enjoy it, everyone’s loving it which is great, I just can’t really believe it, still, to be honest,” he said.
Banksy is one of the world’s most famous artists, but his identity remains, officially at least, unknown.
His most famous works include Kissing Coppers (2004) and Girl with Balloon (2006), which was shredded in a stunt following its sale at auction in 2018.
The artist’s most recent known piece, a stop sign with three military drones on it, was stolen just hours after it had been confirmed as authentic in December last year.
In February, two men were re-bailed for theft, with officers still trying to track down the artwork, which was taken from a south London street.
Speaking to BBC Radio 4’s Today programme, Mr Peak said that by incorporating a tree into the artwork, Banksy has “solved an emerging problem” of people trying to steal his work.
“I don’t think anyone is going to be able to nick this… how are you going to steal a tree?”