Rattled by a shaky start to their campaign, Germany's Greens are trying to regroup ahead of next month's general election with a renewed focus on climate protection as floods and fires ravage Europe.

The ecologist party's bid to crown their candidate Annalena Baerbock as Angela Merkel's successor as chancellor seemed to falter this summer over a series of gaffes.

Now hoping to seize on the urgency of the climate issue in many voters' minds, the Greens chose the central city of Hildesheim to launch the "hot phase" on the hustings, as it is known in Germany, ahead of the September 26 poll.

"A lot is at stake with this election" after 16 years of Merkel at the helm, Baerbock told a crowd assembled on the historic town square.

"It's about our future," said Baerbock, stressing that the Greens were ready "to shape it".

Green party candidate for chancellor Annalena Baerbock addresses a rally in Hildesheim, northern Germany
Green party candidate for chancellor Annalena Baerbock addresses a rally in Hildesheim, northern Germany AFP / Ronny Hartmann

Western Germany last month experienced devastating floods that left at least 190 people dead and washed away billions of euros in housing, businesses and public infrastructure.

Meanwhile thousands of German holiday-makers recently returned from Greece after witnessing first-hand raging forest fires.

An alarming UN report said this week that such catastrophes would grow more frequent as global warming is occurring far more quickly than previously forecast.

The Greens, who have been warning of the dangerous impact of fossil fuel emissions since their founding four decades ago, have laid out a "climate protection now" plan as part of their platform.

It includes a proposal to create a "super ministry" for the environment with the power to veto government policies deemed potentially harmful.

A supporter holds a banner reading 'Take climate change seriously - no more compromise'
A supporter holds a banner reading 'Take climate change seriously - no more compromise' AFP / Ronny Hartmann

This year is the first time the Green party, in opposition since 2005, has fielded a candidate to lead the country.

In April, its ambition seemed realistic when it tapped Baerbock, an energetic 40-year-old MP, as their standard bearer.

For weeks the party was leading the polls ahead of Merkel's conservative CDU-CSU alliance, which was hobbled by infighting.

But a failure by Baerbock to declare a pay bonus, inaccuracies on her CV and plagiarism allegations did lasting damage to her credibility and shaved several points off their support.

A Green party supporter holds a bouquet of flowers at the party's rally in Hildesheim, northern Germany
A Green party supporter holds a bouquet of flowers at the party's rally in Hildesheim, northern Germany AFP / Ronny Hartmann

Currently the CDU-CSU is leading the Greens by around a 10-point margin, putting their candidate Armin Laschet in pole position to become Germany's next chancellor after Merkel retires this year.

Rosa Wagner Kroeger, a Greens member in her 50s at the rally in Hildesheim, said she was still confident the party could turn the tide.

"Annalena Baerbock is a strong candidate -- very intelligent. She was attacked because she's a woman," Kroeger said.

"Now we should return to the Greens' issues in the campaign which have a lot to offer."

"Of course the personality of the candidate plays a big role," political scientist Thorsten Faas of the Otto Suhr Institute told AFP.

"But the political agenda does too and the Greens of course have a card to play with the climate, the environment and energy which are their foundational issues -- all the more so after the floods which focused the agenda on the climate."

Voters say they're ready for change after Merkel's long tenure, according to a study released in mid-May by the Allensbach demographic institute.

Sixty percent said they wanted a new government to replace the right-left "grand coalition" made up of the conservatives and the Social Democrats (SPD), as well as a more "ambitious" government, particularly on climate policy.

In Hildesheim, Greens supporters were keeping the faith.

"It's going to be tough but she's good and convincing," Marion Olthoff, 66, said of Baerbock.

"Yes, she's definitely got a chance. And the others are so bad," particularly Laschet, she added with a smile.

The conservative state leader has piled up a series of own-goals in recent weeks, including being caught on camera joking with local officials on a visit to a flood-stricken town and getting ensnared in his own plagiarism scandal.

And given the potential vagaries of coalition building, the election's ultimate outcome is still seen as wide open.

"A lot of things have already happened during this campaign," Faas, the political scientist, said. "And it's certainly not over."