NYT / GARY HALLGREN

Last Christmas, Donna Hoffman, an ardent environmentalist who lives in Austin, Texas, came up with an unlikely gift for each member of her family: an energy-efficient compact fluorescent light bulb.

“I wanted to connect through the gift-giving tradition,” said Hoffman, 45, who works as a coordinator for the Sierra Club. “I also wanted to communicate my own deeply-felt environmental conviction.”

In particular, Hoffman said, she hoped to make a point to her sister, Cynda Reznicek, who works for a construction company that builds “a lot of nasty, old-style fossil fuel-related stuff,” including highways and coal-fired electricity plants.

While Reznicek, 50, found the light bulb an amusing gift, and even useful (she has since replaced all the incandescent bulbs in her house), she said she wondered if the holidays were the time to preach austerity.

“We spent so many years so poor, where we didn’t have the money to do much,” Reznicek said. Now that she and her husband, Steve, a lawyer, are doing better financially, “we’re at the point now where we can be a little more extravagant,” she said. “It’s just a joy.”

Cut back now? With all due respect to her sister, Reznicek said, “We thought she was nuts.”

Frivolity versus severity. Materialism versus sacrifice. Welcome to the “green” holidays.

The holidays have always been an emotionally combustible time for families, bringing together a sometimes volatile mix of siblings, crotchety grandparents and ill-behaved children. But in recent years, a new figure has joined the celebration, to complicate the proceedings even further: the green evangelist of the family — the impassioned activist bent on eradicating the wasteful materialism of the holidays.

Otherwise known, at least to skeptical traditionalists, as the new Grinch.

This Grinch is not out to spoil Christmas, but merely to use it as a platform to advocate ecological responsibility. Perhaps emboldened by the “Live Earth” benefit concerts and Al Gore’s Nobel Peace Prize, this is the family member who is the first to point out, over the bountiful Christmas dinner, that the 2.6 billion holiday cards sold each year in the United States could fill a landfill the size of a football field 10 stories high, or that those conventional lights on the Christmas tree contribute up to nine times as much greenhouse-gas emissions as the leaner-burning LED models; or that some Christmas-tree growers use as many as 40 different pesticides, as well as chemical colorants, on their crops.

The question that an increasing number of families face is whether the proselytizing green member of the clan adds spice to the proceeding, like, say, a cup of whiskey in a bowl of eggnog, or an explosive element, like that same cup of whiskey tossed into the fire on Christmas morning.

It’s not just the greens who feel this emotional tug at the end of the year: A 2005 survey by the Center for a New American Dream showed that 78 percent of Americans wish the holidays were “less materialistic.” At the same time, the average American spends about $900 on presents each year, according to the National Retail Federation.

Still, to some ears, the call for less excessive consumption during the holidays sounds almost un-American.

“The point of the holidays for many people is the joy people get in giving,” said Kenneth P. Green, a resident scholar on environmental issues at the American Enterprise Institute. Environmentalists who scold their families are simply making “ritualistic gestures that won’t solve the problem,” he said.

The concept of a green holiday is so new, said Amanda Freeman, a founder of the environmental Web site Vitaljuicedaily.com, that no one has yet codified the etiquette. “I think you have to watch the line between giving people helpful tips they may not know about, and criticizing everything they do.” The drama is heightened because “everyone already feels pressure this time of year,” said Pauline Wallin, a clinical psychologist in Camp Hill, Pa., “When somebody comes in and starts preaching, it’s one more thing they have to think about.”

Indeed, Claire Roby, a senior majoring in environmental studies at American University in Washington, said she is already preparing for conflict when she travels home to Oklahoma this Christmas. Roby plans to spread the green message with the gifts she gives: handmade clocks made from discarded CDs and scavenged electronic components, wrapped in newspaper.

“We’ll see how much we can avoid a dinner table argument this year,” Roby, 22, said. Wallin said that environmental activists can avoid arguments by trying to lead by example, not by lecture. “Don’t force them to change,” she said.

“It may take two or three seasons, but you are not going to get anywhere by showing up and thumbing your nose.”