"They have come up with ways to bomb the trees pretty quickly and shrink back into the shadows."
Mr Hart said there would be a "spectacular surprise" this year.
"It's going to be pretty awesome and might put Greerton Village on the national map."
Greerton was known internationally on yarn artist websites, he said. The installation would be in place for about six weeks. "The narrative is that we have no idea who the shadowy figures are who do the yarn-bombing," he said.
"Greerton Guerrillas have hinted that it will be about happy colours and warming up winter days."
There were about six people in the Greerton Guerrillas group, who had been engaging with wider Tauranga for the project, he said.
Mr Hart said retirement villages had submitted yarn.
There would be one tree done by the Ninja Knits in the Historic Village, he said.
"It's about bringing a bit of colour to the village, to what's traditionally a cold and grey period of time.
"Tauranga is known as a summer-time destination. But out here in Greerton Village we try warm up things in midwinter as well," he said.