Acting Detective Sergeant Greg Johnson, who headed the investigation, said the 18-year-old was arrested on January 23 and remanded in custody until February 12. He was also charged with two burglaries of commercial buildings in Kawakawa.
The other accused are too young to be charged in the district court.
Mr Johnson said it was sad that young people had been involved in the arson attacks.
"It is a very serious offence carrying a hefty penalty, but it is also such a danger to human life. Not only are they putting their own lives in jeopardy - they are risking the lives of their own whanau and community who turn out as volunteer firefighters."
Mr Johnson said police now had a "pretty clear picture" of who was responsible for the fires and would continue their inquiries this week.
"The most important thing for us has been stopping this behaviour before someone gets seriously hurt. We and the fire service will be taking a prevention approach with these kids and their families, making sure this doesn't happen again."
Kawakawa fire chief Wayne Martin was relieved to hear of the arrest. The repeated call-outs had been tough on the volunteers and their employers, and had put the firefighters in danger.
"Our lives were being put at risk through someone's stupidity ... The arrest is good work by the police, with help from members of the community," he said.
A fire which destroyed a double garage and a prized BMW on Derrick Rd last week was found to have been caused by an electrical fault.
