A 'GRANDIOSE' idea by a Northern Rivers farmer to grow cannabis and then use the funds to restock his acreage with native trees and buy chickens backfired when police discovered his secret stash with a street value of $556,000.

Peter Stear Jackson, a grandfather from Koonorigan, was sentenced to 18 months of weekend detention after pleading guilty in Lismore District Court to growing and commercial supply charges, involving 134 cannabis plants, 25.9kg of cannabis leaf and head, 1.067kg of cannabis resin, and 577 cannabis seeds.

When police discovered the drugs on May 1, 2008, Jackson told the officers he only smoked cannabis 'once a year' at the annual Nimbin Mardi Grass festival.

Defence lawyer Ralph James successfully argued for a minimum sentence on the grounds that medical evidence including psychiatric reports revealed his client had been having mental health problems (a bipolar disorder), suffering severe depression, and having 'grandiose thoughts' during a hypermanic episode involving substantial departure from reality.

“He says it (cannabis) was for a specific purpose, but there is no trafficking,” Mr James said.

The Crown agreed Jackson's mental health was relevant in assessing his moral culpability, but alone was not enough to move the case to the realm of exceptional circumstances.

He had known what he was doing and that it was wrong, and a 20-litre tub was found under his house filled with cannabis leaf and head.

Judge James Black said he accepted Jackson was unlikely to re- offend, had no record of offences, was of good character, with clear evidence he was 'a good man in the community', and also took into account the medical matters.