WEST LAFAYETTE, Ind. — This holiday season could be especially “green” as tree growers anticipate a busy 2013 sales period, partly because of the public’s increasing concern for the environment, a Purdue Extension wood products specialist said.

Still, the debate over whether real trees or artificial trees are better for the environment continues, said Daniel Cassens, a professor of forestry and natural resources.

“The season is off to an excellent start, with the shorter selling season between Thanksgiving and Christmas partially responsible,” said Cassens, who also is a member of the National Christmas Tree Growers Association.

Thanksgiving, on Nov. 28, was a few days later than usual this year.

More than $1 billion in real trees will be sold in the U.S., the vast majority from Thanksgiving weekend through the first two weeks of December, Cassens said.

About 28 million real trees are sold in the U.S. each year, and 200,000 choose-and-cut Christmas trees will be sold in Indiana this year.

While many customers return to farms each year to cut their own tree because of the enjoyable family experience, Cassens said he is seeing two categories of new customers:

* Young couples or singles who have never had a real tree before — Purdue Extension has a free publication, Tips for First-time Buyers of Real Christmas Trees , available at mdc.itap.purdue.edu/item.asp?itemID19820.

Cassens suggested that people needing more information about Christmas trees or how to find a choose-and-cut tree farm should visit the National Christmas Tree Growers Association website at www.realchristmastrees.org; and

* Those concerned about the environment — Cassens noted tree growers point out that their product is renewable, each species has its own characteristic odor, consumes carbon dioxide and gives off oxygen, can be recycled, provides wildlife habitat and creates jobs in rural America.

Artificial trees contain non-biodegradable plastics and possible metal toxins, and most are made outside the U.S. and must be shipped long distances, he said.

The artificial-tree industry, however, points out that its product can be reused, saving real trees from being cut down, Cassens said. The industry also notes that its trees do not need fertilizers or pesticides.

“These are just examples of claims being made by two distinctly different industries,” Cassens said.

It is difficult to determine which type of tree is better for the environment because there is only one documented study comparing how they impact the environment, specifically in the amount of carbon dioxide attributed to them, Cassens said. That study was done in 2009 by the Canadian environmental consulting company Ellipsos Inc.

Carbon dioxide is important because it traps heat from the Earth’s surface in what is commonly called the “greenhouse effect.”

The study concluded that a 7-foot real Christmas tree grown south of Montreal accounted for 53 pounds of carbon dioxide after all production factors such as labor, use of machinery and transportation were considered. The study assumed that the tree was grown in a nursery for four years and in a field for 11 years.

Cassens said a 7-foot Indiana tree probably would result in less carbon being released because such a tree typically comes from 2-year-old nursery stock and grows in a field for about seven years.

The carbon dioxide associated with a 6-foot artificial tree, according to the study, amounted to 106 pounds — twice as much as the real tree.

Cassens noted that most of the carbon release was from the manufacturing and transportation of the tree by ship from China to Vancouver and then by train to Montreal.

“The study goes on to conclude that considering climate change impact along with environmental and public health impact, real trees appear to be a better choice for a responsible customer and that artificial trees must be displayed for more than 20 years in order for it to compare favorably with the real Christmas tree,” he said.