"Hopefully we'll get enough kumara to feed a lot of people out there," Allan, inmate of 13 years says.

Prisoners are giving "the best food there is" for Christmas.

Allan, which is not his real name, along with dozens of Auckland Prison inmates are growing tons of veges to donate to charities.

The inmate of 13 years has worked the last six years of his sentence learning horticultural skills he hopes to put to use when released.

SIMON MAUDE/FAIRFAX NZ Te Piriti prison unit tutors and guards Bill Bean, left, and Don Gillanders. Allan planted the marigolds.

"I want to leave prison with a degree in horticulture," Allan says.

Along the way the Allan has helped instruct other prisoners on improved kumara cultivation methods he developed.

"This is a number 8 type wire nursery, but our growing rates are extremely high," he says.

Allan proudly shows off another project he's involved in.

"Look at this, a rainforest worth of manuka seed!"

He's cupping a container holding around 250,000 of the honey producing tree's seeds.

Veges grown by the inmates at the sprawling Paremoremo prison north of Auckland are snapped up by Women's Refuge and Salvation Army.

Prison guard and horticulture instructor Jason Maxwell says Paremoremo's 'Te Piriti' or 'The Bridge' programme can't keep up with demand.

"The gardens have become part of prisoner therapy," Maxwell says.

Maxwell, who has worked with hundreds of violent and nonviolent offenders in the programme, says growing food for charities is one way prisoners can make amends to society.

Inmates also receive treatment from qualified therapists as part of weekly progress assessments.

Apart from vege gardening, inmates can gain NCEA credits learning composting, landscaping and nursery skills, Maxwell says.

Prisoners grow more than 20 vege types through the seasons.

Combined with Maxwell, prison guards Bill 'Mr' Bean and Don Gillanders bring about 50 years of horticultural experience to Te Piriti.

Maxwell credits Bean with growing the gardens and nursery to its several hectares that ring the dormitory style prison unit.

Bean was a guard for 20 years before becoming an instructor.

"[Being a guard means] having the skills and understanding of how to relate to an inmate, treat them firm but treat them fair," Bean says.

Instructor Don Gillanders says he gets "quite a lot of satisfaction" from helping prisoners learn.

"If they weren't doing this they would be sitting in their cells doing nothing."

And Allan's glad about that.

"If it weren't for Bill and the other instructors giving me a chance, I wouldn't know where I'd be."