For the past three Aprils, a mishmash of musicians, activists and members of Congress have gathered on the Mall to celebrate Earth Day, encouraging Americans to go green.

This year, they’ll go silent. The Earth Day Network, the nonprofit organization behind the annual celebration, says it won’t be hosting its annual flagship event this year because it overlaps with the Easter and Passover holidays.

“So many of the congressional members that participate would be gone,” said Earth Day Network President Kathleen Rogers. “ We could have done it in May, but we thought it was best to focus on next year.”

Rogers said 2012’s event will be themed “The Road to Rio” in anticipation of the international Earth Summit scheduled to take place in Rio de Janiero next June. “Our intention is to make the event on the Mall really global,” Rogers said of next April’s Washington celebration. And that means bringing more international stars to the stage.

Earth Day events have taken place on the Mall on and off since the first Earth Day in 1970, but in terms of pop music star power, the event has gained considerable momentum over the past three years. In 2008, hip-hop group the Roots, reggae vets Toots and the Maytals and Washington’s own Thievery Corporation were scheduled to perform before Mother Nature intervened with an electrical storm that cut the program short.

April 2009 provided sunnier skies and performances from Chicano rockers Los Lobos and heartland psych-troupe the Flaming Lips. And last year’s event brought sets from former Police-man Sting, soul icon Mavis Staples, reggae legend Jimmy Cliff, R&B singer John Legend, the Roots and others.

But don’t call it a concert. The Earth Day Network’s annual celebration is a “First Amendment event,” meaning that 60 percent of the program must be dedicated to oratory, leaving 40 percent for entertainment, Rogers said. This explains the brief musical sets and long-winded speeches that have defined the event.

Next year, the music — and the speeches — are scheduled to return.

“We don’t want to turn Earth Day into a straight music event,” Rogers said.