Carol Pine (40) says she wants the Government to make synthetic cannabis illegal because it is ''killing'' her son, David Pine (20).
She had previously found her son high on synthetic cannabis and eating lasagne off the kitchen floor with his hands, she said.
Her son slept in a caravan outside her house and had ''convulsions'' when high on synthetic cannabis, she said.
''One day, we had to ring an ambulance because he was lying in the gutter out the front of the house,'' she said.
Late last month, he could not pay all his board because he had bought synthetic cannabis, so one morning she told him to pack up and leave, she said.
''I thought it would put the fear of God in him.''
He left and returned in the afternoon - high, angry and demanding money, she said.
''He towered right over me and he was spitting at me like an animal.''
She said he had made threats against her and other family members. Police arrived and took him away, she said.
''That's not my son. That's a monster, a K2 monster.''
He spent his 20th birthday earlier this month in the ''Milton Hilton'' - the Otago Corrections Facility, near Milton, she said.
''He rang me crying. He said 'Mum, I don't like it here; you've got to get me out'.''
She would not post his bail because she wanted him to get drug rehabilitation, Mrs Pine said.
Police had told her the only way her son could be rehabilitated was by being ''locked up''.
''We are having to send our children to prison to get help. What's with that?''
He overcame a minor alcohol problem about two years ago when his son was born, she said.
''He had everything going for him. He was really, really good.''
Her son then started smoking synthetic cannabis - about $80 worth a week - and became addicted about 18 months ago, she said.
Last month, a man came to her door to collect a synthetic cannabis debt for a local shop, she said.
The man said her son was ''ticking it up'' and gave her a handwritten bill of $75.50, she said.
A spokesman for the shop declined to comment on Mrs Pine's allegations. Mrs Pine said she had not paid the debt but would stand by her son.
''He is my son. He will always be my son.''
She has started a petition to have synthetic cannabis made illegal and has collected 250 signatures.
''They say they are going to review this in August. Why wait 'til then? Why not do it tomorrow? It's killing our kids. It has got to stop.''
Senior Sergeant Darryl Lennane, of Mosgiel, said he was unaware of any shops allowing customers to ''tick up'' synthetic cannabis.
If stores were selling ''on tick'' they were not breaking the law, he said.
However, police visited shops to encourage a ''socially responsible approach'' to selling synthetic cannabis, he said.
''But a lot of them are of the view that they are making money out of it and they'll continue to do so.''
Dunedin Women's Refuge community outreach worker Amanda Durham said synthetic cannabis regularly featured in police reports relating to the abuse of parents by teenagers.
The domestic violence occurred when there was no money available to buy synthetic cannabis, she said.
• David Pine is in custody for alleged intimidation and is due to appear in the Dunedin District Court on Tuesday.
• United Future leader Peter Dunne's Psychoactive Substances Bill passed its first reading in Parliament earlier this month, with the support of all parties. The Bill proposes to make all psychoactive substances illegal, unless the industry can prove its products carry a low risk.
