Christmas trees, a ubiquitous part of the holiday season, for many, are more than a depository for presents. They are an industry unto themselves.

Approximately 27 million real trees with a retail value of $976 million were sold in the U.S. in 2010, according to the National Christmas Tree Association, and many of the 15,000 tree farms across the country have been run by the same family for generations.

Bruce Tammen was raised in the Christmas tree business. His father first planted trees in 1956 when some of the land on their farm in Wilmington, Ill., proved unsuitable for growing crops. What started in a small field grew to become the 150-acre Treeberry Farm, where Tammen grows several varieties of evergreen trees and blueberries.

The process of raising trees requires many areas of expertise, according to Tammen, including a detailed knowledge of soil, biology and many agricultural practices. He said patience is also important, especially in an industry where it can take up to 10 years to see any revenue.

Tammen and his two full-time employees tend to the trees year-round. Younger trees require fertilizer and are treated with herbicide to prevent surrounding grass from blocking the sunlight. When the trees grow to be waist-high, they are sheared by hand with large blades to create the symmetrical taper customers want.

“It’s a difficult business,” Tammen said. “Most people don’t realize how much work is involved in it.”

Tammen sells his trees by letting customers come to the farm to choose and cut their own. He said he has seen multiple generations of families in the 35 years he has been running the farm.

“Many of my customers came here when they were children,” he said. “Now, they have their own families and are carrying on the tradition.”

According to the U.S. Department of Agriculture’s most recent census, Illinois has nearly 300 tree farms that harvested more than 112,000 trees. Many of the trees sold in the state are shipped from other locations, said David Daniken, former president and current board member of the Illinois Christmas Tree Association.

“Illinois is dominated by small choose- and-cut style farms,” Daniken said. “Weather conditions here are not ideal for growing massive quantities of plantation-grown Christmas trees like they do in parts of Michigan, Pennsylvania, North Carolina, Washington and Oregon.”

Daniken, a second-generation tree farmer with a 60-acre operation in Pocahontas, Ill., said he supplements the trees he grows with varieties harvested in other states. Fraser and noble firs—two popular trees that are difficult to grow in Illinois—are brought in from Michigan and Oregon.

Like Tammen, Daniken said the bulk of his business comes from customers visiting his farm to cut their own trees. Although visiting a tree farm ensures a fresh tree, Daniken said the industry as a whole has become very responsive to shifting demand.

“These days, most trees are very well-kept, cut very late in the season and typically very fresh when they get to you,” he said. “Whether it’s a big-box retailer or a tree lot, or buying a pre-cut tree at a farm, you’re going to get a good product.”

Amber Arneson’s family has been selling Christmas trees in Chicago for more than 65 years.

Today, she and her husband operate eight lots around the city that sell trees brought down from small farms in Wisconsin. In order to find the best selection, Arneson said she spends months personally selecting and tagging each tree before it is cut.

Although she chooses a variety of trees to harvest, she said Chicagoans have a clear preference for what they want in their homes.

“Balsam has always been the most popular because its [branches] are very strong and fragrant,” Arneson said. “But Frasers have also been selling well. They have a beautiful color and hold ornaments well. They’re becoming more and more popular every year, especially in Chicago.”

She said her business is selling half the amount of trees it did 30 years ago, a drop she attributes to the increasing popularity of big-box retailers that are able to order massive numbers of trees from large-scale farms at lower prices.

“We can’t compete with [large retailers] because they sell trees cheaper than we actually buy them at wholesale,” Arneson said.

Demand for live trees has also been affected by the popularity of artificial trees, she said. Although artificial trees are convenient, according to Arneson, she believes they do little to support the economy.

“When you buy an artificial tree, the money just goes to the corporations and the country where it was manufactured,” she said. “With real trees, this is money that was made in America, stays in America and supports American people.”