For the Green Party, so long confined to the sidelines of power, it must be like one of those cruelly simple childhood games – musical chairs, or pass the parcel.

One day last October, Winston Peters declares to a waiting nation that he can live with the Greens being part of a NZ First/Labour government coalition. And suddenly it is all on.

Three ministers outside Cabinet and a parliamentary under-secretary is the supply and confidence deal. The music stopped and the baubles of office dished out to whichever Green MPs happened to be Johnny on the spot.

So not Russel Norman, Kevin Hague, Metiria Turei, Kennedy Graham, David Clendon, Mojo Mathers, or the long list of others who managed to fall off the party train for one reason or another.

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Instead, co-leader James Shaw took minister for climate change for himself. Then into the lap of Eugenie Sage – sensible glasses, cautious smile – fell the plums of minister of conservation, minister of land information, and associate minister for the environment.

Eugenie who? Before this year, Sage would have barely registered with the New Zealand public. Now here she is, about to be judged on the legacy she can create while being in receipt of the gift of a set of core green portfolios.

Is she still pinching herself at this unexpected turn of events? Sage almost chokes with laughter when recalling the moment it actually happened.

"We were watching Mr Peters on the news at that live press conference, and then we went into our teleconference with over 120 Green Party delegates to decide whether to go in. It was a surprise," she trails off in happy reminiscence.

The human drama of power. Sage says what struck her was the abrupt switch from being on the outside looking in – stalled for six months by the sitting minister on every information request – to having a staff ready to jump on any question.

And Sage looks to have hit the ground running.

Despite her dislike of the attention – "Why do you want to interview another boring minister?" are the first words of the interview – she is fronting some environment story or another most days now.

Yet can Sage construct a legacy? How much advantage will the Greens be able to wring from what could be just a fleeting single-term opportunity?

THE LONG APPRENTICESHIP

Safe to say that 59-year-old Sage cuts quite a different figure to her predecessor, broadcaster Maggie Barry.

Unobtrusive is the word that springs to mind. But a glance at her CV suggests she could be the best prepared conservation minister ever.

PETER DRURY/STUFF Missing out: Sage with former Greens co-leader Russel Norman in 2014. Some people's turn never came.

In the South Island especially, Sage will know where everybody has been buried for the past 30 years or so.

The daughter of an Auckland chartered accountant, she was raised in a bushy corner of the eastern suburbs.

"I was lucky enough to grow up in a section with a gully and a stream at the bottom of it. I used to climb trees to get away from my younger brothers, or muck around in the stream."

So a normal, outdoorsy, hard-tramping, Kiwi then. Box ticked.

Sage did law at Auckland University and followed that with journalism at Canterbury University. There was a stint writing for Craccum and some mild student activism.

"My first environmental protest was against McDonald's opening in Queen St – it's still in the same place, I think."

But Sage wasn't a "chain yourself to trees" eco-warrior. Her first job was as an information officer for the New Zealand Forest Service on the West Coast.

That was schizophrenic, she says. On the one hand, the service was "napalming" the ancient beech forests. On the other, she was promoting the area's historic and natural heritage.

Next came a researcher position with the Labour Party. By the late 1980s, she was Helen Clark's press secretary at a time Clark was minister for conservation.

The DOC connections continue. Her partner is long-serving DOC manager Richard Suggate. Sage moved south to Christchurch with him and his son in 1990, settling on Banks Peninsula.

That led to a job as a spokesperson with Forest & Bird. For 13 years, she had a ringside seat on one South Island environmental battle after another. Tenure review, the Timberlands logging scheme, manuka clearances, kea, wetlands, hector's dolphins, the Pike River coal mine.

Sage then became an Environment Canterbury (ECan) councillor, standing on a water platform. So – until Nick Smith sacked the council in 2010 and installed government commissioners – she was ringside on Canterbury's irrigation wars too.

A further lesson in real-life policy making to add to her resume.

Recognising her knowledge, Green Party leaders shoulder-tapped her for the 2011 general election. Ranked a high six on the party list, she found herself in opposition as an MP.

"So I've had a long apprenticeship. I had no ambitions to be a politician, but one thing has sort of led to another," she says.

And now – being clearly far from green about the mechanics of government – she is ready to get stuff done.

EACH PORTFOLIO ITS OWN STORY

What is on the agenda? First off, Sage says something else going her way is that she believes the New Zealand public is hungry for real change.

The coalition's motto is "inclusive and sustainable". And that neatly sums up its social and environmental ambitions.

Coming to her portfolios, each presents a somewhat different political challenge.

As land information minister, she is coming in at the tail end of the tenure review saga, for example. The horse has largely bolted in terms of selling off high country leases. But she still needs to tidy up what remains.

NICHOLAS BOYACK/STUFF Troublesome plastic: China has sparked a recycling crisis by no longer taking our waste.

Then DOC is another stage in the story. The priority there has been to get it the funding to do its job properly as an advocate for the conservation estate.

Sage says the voice of DOC had been neutered by nearly a decade of National rule. "It was seen as controversial and cutting across the aspirations of developers."

Funding restrictions meant it contracted by about 220 staff. "There was a loss of huge amount of technical expertise – resource lawyers, technical ecologists, programme managers."

So at consent hearings and council plan submissions, DOC had simply gone missing in action.

Sage says in the May Budget, she won a $181m boost over four years for her department. The most important step was thus just getting DOC back into business again.

Her third portfolio is associate environment minister. And now this is where she can be in at the beginning of something new.

This year China has sparked an international waste management crisis by ceasing to accept other people's rubbish for recycling.

Suddenly New Zealand can't just export its crushed bales of plastic bottles. These are now piling up in our council tips.

So there is a full-on problem, says Sage. And the country has to step back from its "out of sight, out of mind" approach to old tyres, e-waste, lithium batteries, and other recycling issues too.

The moment is ripe for a lasting national framework that can deal with our waste in a sustainable manner – the creation of new laws, new industries.

"Auckland – they don't have an organics collection yet," Sage exclaims. It might be coming in 2020, but it shows how far behind green ideals the country drags.

Last question. Sage's best and worst moment so far?

Definitely the darkest was having to allow Chinese water bottling giant Nongfu Spring to expand its existing Bay of Plenty operation, she says.

As land information minister – and understanding how the law works – there was no choice. Anything else would have left the department liable to judicial review.

But seeing the pen in her hand, her hand actually signing the document, that is when the personal sense of betrayal hit.

The best moment was the enthusiastic briefing from a DOC pest programme manager talking about being able to organise 1080 drops without having to go cap in hand for the budget each year.

It was the flow-on effect. DOC could give its helicopter companies and other contractors the same security to invest in their own staff and businesses. "Now he can just focus on the job rather than worrying about whether the funding will be there to do his job."

A warm fuzzy feeling as minister. Again, the very human drama of suddenly finding yourself the one on the inside, now looking out.