The sophisticated farm was found in a disused care home, known as Unity House, in Llandrinio near Welshpool on May 31, 2016.
Endrit Rusta, 32, was arrested at the premises after a police tip-off.
The police investigation found that he had made numerous trips to the site driving a car hired from a company based in Telford.
They also uncovered CCTV evidence of him buying food and staples in shops in Shrewsbury, and the receipts were discovered during a search of the house. There was evidence of staples used to fasten plastic sheets at the house.
However, the hearing at Mold Crown Court was told that Rusta later failed to turn up at an hearing before magistrates, resulting in the case only now being concluded after five years.
The Albanian national pleaded guilty to being concerned in the production of cannabis, on the basis that he was not involved in the setting up or running of the operation at the former rectory.
At a hearing on Thursday, Mr Sion ap Mihangel, prosecuting, said the basis was not accepted by the crown.
He said the haul comprising 866 cuttings and 112 plants had been valued at £440,000 by police drugs experts.
Giving evidence Rusta said at the time he was not allowed to work in this country and had no money. He said he was offered gardening jobs by a man called Luciano who then paid him £100 a time to drive the care to Llandrinio on errands.
“He asked me to go there for a few hours to check round and make sure the doors and windows were closed. After the third time I became aware that cannabis was being grown there,” Rusta said.
Eiran Reilly, defending Rusta, said that the defendant was remorseful of his actions and that there was insufficient evidence to show that he played a significant role in the operation.
Judge Timothy Petts told Rusta: “I do not entirely accept your version of events. The custody threshold has been passed. I accept that immediate custody will impact on your ex-part and children.
“Those who get involved as you have done with full scale production of a significant amount of cannabis cannot complain if immediate custody is the outcome.”
Rusta, of Stanmore Road, Edgbaston, Birmingham, was jailed for 18 months. He must serve half before being released on licence.
He also ordered the forfeiture and destruction of the drugs and the equipment seized from Unity House.