Long-time co-leader Jeanette Fitzsimons announced yesterday she would relinquish the co-leadership, opening the way for Ms Turei, from Dunedin, to seek election.
The Greens select their leaders in a widely democratic way with each electorate sending two candidates to the conference to vote.
The leadership will be decided by the STV (single transferable vote) system.
Other political parties allow their own caucus to select their leaders and deputy leaders.
The Greens have a male and female co-leader and co-president.
Ms Turei and MP Sue Bradford have indicated they will seek the co-leadership role, but the Otago Daily Times understands that at least two women from outside Parliament will be campaigning for election.
Co-leader Russel Norman was elected from outside the Parliamentary ranks when former leader Rod Donald died.
Dr Norman entered Parliament on the list when Nandor Tanzcos retired from Parliament.
Ms Turei said yesterday she would give up being the Green Party "musterer", or whip, in Parliament so she could campaign around the country.
"That's good. 'We should make ourselves available to party members.
''We are a party that operates with a grass-roots leadership.
''The leader has to facilitate leadership roles throughout the party instead of being the sole decision-maker."
The Greens were becoming a "broader church" party.
Polling showed New Zealanders, across the political spectrum, wanted to see a green presence in policies.
The new co-leader would have to deal with the growth and changing nature of membership, she said.
There could be a move towards the middle of the political spectrum and those political tensions would need to be managed.
"Jeanette did us the very best service by stepping down now so we can make changes and deal with them in the next two to three years," Ms Turei said.
Ms Fitzsimons said the party had always attracted competent women and she was confident the party would be spoiled for choice in June with several strong contenders for the position.
Ms Fitzsimons was elected to the co-leadership with Mr Donald 14 years ago, when the party first created the positions.
She won the Coromandel electorate in 1999 but since 2002, has been a list MP.
It is likely she will retire from politics before the election.
David Clendon, who stood in Helensville against Prime Minister John Key, is the next on the party's list.
Both Mr Key and Opposition leader Phil Goff paid tribute to Ms Fitzsimons.
Mr Key said that even though he and Ms Fitzsimons had not always agreed on policy positions, he respected the way she had carried out her role with integrity and belief.
"She has been a long-serving and effective leader for the Green Party, and only last week I enjoyed meeting with her and co-leader Russel Norman to discuss areas where we might be able to work together," he said.
Mr Goff said Ms Fitzsimons was a talented and capable politician, never afraid to weather sometimes weighty criticism in order to advance debate about the issues she felt passionately about, such as climate change.
