A food activist has been convicted for illegally importing plants and seeds from overseas in what he says was an attempt to protect New Zealand's food sources from the threat of genetic modification.

Kyle Arthur, 30, was caught by biosecurity officials sneaking consignments of "wild, heritage, and heirloom non-genetically engineered plants and seeds" without permission from the Ministry of Primary Industries (MPI).

A raid on his Christchurch found he'd illegally imported papaya, mango, jackfruit, tamarind and banana between October 2017 and June last year.

The musician was charged for breaches under the Biosecurity Act, which carries a maximum penalty of five years' imprisonment or a $100,000 fine.

Arthur had earlier sought a discharge without conviction, telling a Christchurch District Court judge that a criminal blemish would stop him from travelling to various overseas countries and continuing his quest to legally source GM-free plants and seeds.

But Judge Tony Couch dismissed the application for a discharge, finding that his offending was undoubtedly "serious offences against the Biosecurity Act".

Defence counsel Nikita Mitskevich today said Arthur was "motivated by altruism" but accepted that it was "ultimately misguided".

He was "incredibly passionate" about his seeds and plants and had "essentially thrown his life behind" the task.

Judge Couch accepted that Arthur was motivated by genuine concerns that New Zealand's plant diversity and purity is endangered by increasing genetic modification, and not by a wish to harm the ecosystem or personally profit.

The court heard how Arthur asked suppliers abroad to falsely described the plants and seeds variously as decorations, educational items, beauty products, and toys.

Arthur then sold the unauthorised material, largely through Trade Me, encouraging members of public to propagate and grow the plants.

Judge Couch ruled that his actions were an obvious danger to New Zealand's native flora, with the offending also carrying the risk of bringing in diseases or parasites.

He cited the "classic example" of the intentional introduction of gorse, which had displaced native species and the unintentional introduction of didymo and the Queensland fruit fly.

Since the charges have been laid, Arthur has imported further plant material legitimately.

Judge Couch said that showed he's not prevented from doing it, he just needs to do it legally.

He sentenced Arthur to six months' community detention, with a daily curfew of 7pm-7am, as well as 100 hours of community work.