A pensioner grew cannabis with a street value of £12,000 to pay for a drugs rehabilitation course for his son, a court heard.Frank Jones, 74, a former oil rig worker, admitted producing nearly 400 grams of cannabis.He told Barnsley Magistrates Court he believed the plants were worth only £2,000-£3,000 and he got the idea to grow them from a fellow gardener.Mr Jones admitted he knew selling the plants he grew at his home in Worsbrough Common, Barnsley would be illegal.But he said after the hearing: 'You tell me any parent who sees their son suffering who would not do just about anything to help them.'Not that I ever worked out how I would sell them or how I would find someone to offer me money for them.'He said he was 'gobsmacked' that the plants were worth so much and that he would face legal proceedings.Mr Jones added: 'I used to work in Amsterdam and was offered cannabis to smoke and said 'no'. Now I'm being branded as some sort of big time drug dealer.'They said in court the plants I grew had a value of almost £12,000. What - just from a packet of seeds?'All I wanted to do was make £2,500 to get my son into rehab because he has a serious drugs problem.'Are they telling me those plants are worth all that money? To be honest it was as easy growing them as tomatoes.'I'm no drug dealer and when the police came to the house and took them away I didn't think I had anything to worry about. 'When the letter arrived saying I had to go to court and I learned what i was charged with I was gobsmacked.'He will be sentenced at a later date.