Two 4 Seasons workers caught on camera outside the young mother's house, whom they later threatened.
The young mum, who did not want to be identified, believed they were not a genuine company after she viewed them on security camera footage looking around the front of her property.
Her partner had earlier told them to go away. The young mum then posted images of the group on the Halswell Community page with a warning that they "don't look legit".
That prompted a response from the tree cutters in a private message to the young mum: "We know where you live. We're coming over for you motherf****** and cut your f****** head off."
They followed that up with another message stressing they were a bona fide company.
The young mum told the Star: "They said they know where I live and . . . I thought 'oh my god I think they are waiting for me at my house'."
Senior Constable Deb Smalley said an investigation had determined there was no danger to the young mum and the beheading threat was hollow.
She said the threat was a "typical example of trash talk" on social media.
Police had ordered the two women responsible to apologise to the young mum – which still has not happened.
"It's a couple of young women talking nonsense who will be held accountable for their actions," Senior Constable Smalley said.
The young mum wants the pair charged. One of the women who posted the threat told The Star: "I wasn't happy that she put our faces on social media. I didn't mean to say it but I was really angry at the time.
"I'm not going to do it [cut her head off], but I was saying it to make her scared of putting it on Facebook."
The owner of 4 Seasons Tree Lopping Services, Danny Scanlan, said his staff will apologise for their threats. He said he is sorry for what happened.
He also denied claims his company was not genuine and was unaware of another arborist company in Christchurch called Four Seasons Tree Care.
His company was not registered, but that would change soon, said Scanlan.
"The 4 Seasons [Tree Lopping Services] we're doing is the one that my uncle used to do. When he moved to Brisbane I was taking over the 4 Seasons," Scanlan said.