Buoyed by public anger at Chancellor Angela Merkel's nuclear policy after she decided to extend the life of Germany's 17 nuclear reactors, the Green party is powering ahead in the opinion polls.
Party co-president Claudia Roth denounced the "nuclear putsch of the country's conservatives and liberals" linked to the federal government and its nuclear strategy.
The policy was simply a means of allowing big energy companies to earn "70 billion euros" added Cem Ozdemir, the other co-president.
Over the past few weeks, and for the first time, the Greens have drawn nearly level with the Social Democrats (SPD), the main opposition party with which it formed a government from 1998 to 2005.
The Greens have been scoring over 20 percent in voting intentions, compared with the 10.7 percent of votes it actually received in the 2009 general election.
The three-day conference, held under the slogan "Mission: Green", will debate policy and re-elect joint leaders Claudia Roth and Cem Ozdemir.
The party has high hopes for several of next year's six regional elections, including in Baden-Württemberg where its annual conference is being held.
The southwest German state has long been a conservative bastion, but recent polling suggests the Greens could capture some 30 percent of the vote there on March 27.
The controversial Stuttgart 21 building project at the railway station in the regional capital has led to mounting opposition to the local government.
The party, which has not won a regional election since it was founded in 1980, is also expected to do well in September when Berlin, currently led by the SPD, holds its own state election.
Some party stalwarts fear however, the Greens might wither, should they abandon their left-wing roots to move to the centre.
"We would lose massively (in voting) if we renounced our left-wing agenda," Jürgen Trittin, a former environment minister and a co-chair of the Green parliamentary faction, told the Frankfurter Rundschau daily.