Researchers Are Out to Take a Bite Out of a Big Challenge for Christmas Tree Growers: Deer

Many of us count ourselves lucky when we spot a deer. For Christmas tree growers, not so much. Overnight, a hungry deer can cut a young fir tree down to a pencil-sized stem, and even light browsing can set the trees’ growth back by years.

At North Carolina State University, researchers are working on a novel way to protect the trees: covering them with a specially designed fabric that deters the deer, while letting in the light, air and water the trees need to survive.

Raoul Farer, executive deputy director of NC State’s Nonwovens Institute and an expert in textile engineering and fiber and polymer science, has teamed up with Justin Whitehill, leader of the university’s Christmas tree genetics program, to develop the fabric and test it on Fraser fir farms in the North Carolina mountains.

“The idea is that if we make (the fabric) into a cone shape, then drape it over baby trees, the deer will go sniff at it, figure out that the fabric is going to be too complicated to deal with and just move on to eat something else,” Farer says.

Farer sees fabric coverings as a promising way to help Christmas tree growers get a handle on deer browse – now considered one of their top challenges.

However, he sees the potential for a much broader impact.

“In the end, the holy grail that we’re chasing is not just deer browse protection,” Farer says. “We want to develop a fabric that also protects the Christmas trees from all the other bad things that attack it.”

Focusing on Fraser Firs

Farer and Whitehill, both faculty affiliates of the N.C. Plant Sciences Initiative, have homed in on Fraser firs because the trees are highly prized by consumers and white-tailed deer alike.

North Carolina ranks second in the nation for Christmas tree production, generating $144 million in farm income annually from the trees alone, plus more from value-added products like wreaths. And most of that comes from Fraser firs.

Native to high elevations of southern Appalachia, the species accounts for 35% of the total U.S. market. Consumers like Fraser firs because they have a nice aroma, strong branches and a classic shape. They also tend to hold onto their needles.

White-tailed deer are also drawn to Fraser firs in the winter, when other food sources can be scarce. They gravitate toward trees that are less than 3 years old and under 3- to 4-feet high.

Whitehill has been working to address the deer browse challenge on multiple fronts, including breeding trees that are less appealing to deer. His work frequently takes him to tree farms, where he’s seen the damage that the animals can do.

Deer will essentially nip off 50-100% of the buds, and when a hungry herd comes through, they can decimate several acres.

“Deer will essentially nip off 50-100% of the buds, and when a hungry herd comes through, they can decimate several acres,” Whitehill says. “By eating the buds, deer can set the trees’ growth back by two or three years.”

When surviving trees are subject to repeated browsing, they can lose their desired pyramid shape. Growers try to correct the shape by pruning, or shearing, the trees, but that isn’t always successful.

“Most of the time, the growers need to either wait for the trees to correct themselves and get new buds, or most likely they will just reset the whole field with new trees,” Whitehill says.

A Costly Problem Without Easy Solutions

While assessing the economic impact of deer browse is hard, NC State Extension’s Will Kohlway estimates losses of 10% to 15% annually.

“Deer browse is rapidly approaching damage of our No. 1 biotic threat, Phytophthora root rot,” says Kohlway, a Christmas Tree production and marketing specialist. “Anything we can do to reduce the impact of deer will be great for the industry.”

Kohlway sees two trends behind the rising deer browse problem: Hunting isn’t as popular as it once was, and urban development is pushing deer populations toward rural mountain areas.

Deer browse is particularly problematic in Ashe and Alleghany counties, Kohlway says. These northwestern counties lead the state in both Christmas tree production and deer population density, with over 50 deer per square mile.

Sometimes it means you lose the whole tree — it’ll render the tree unsellable.

One Ashe County grower, Tim Moser, says he’s noticed a sharp rise in deer browse damage over the past 10 years.

“Sometimes it means you lose the whole tree — it’ll render the tree unsellable,” says Moser, who operates Shepherd’s Way Farms in Laurel Springs with his wife, Bonnie.

“They’re not just nibbling,” he adds. “It costs us right smart money.”

To help growers like Moser reduce their losses, NC State scientists and tree growers have searched for solutions for years, but all have drawbacks. Fences that are tall enough to keep out deer can be costly to install and maintain, and repellents require frequent applications and can sometimes lose their effectiveness.

Asked about hunting, Moser laughs.

“There’s just too many of them,” he says. “You kill one, and two will come to its funeral.” 

“Anything that we’ve heard might work, we’ve tried,” he adds. Still, “at least 20% of my trees have some damage — and it could be higher.”

Moser has heard of other nearby growers who’ve had luck covering their trees with the type of plastic netting used to package oranges, and he says he’s optimistic that Farer and Whitehill’s could prove successful.

Farer, too, has heard about the orange netting but thinks his solution has advantages: The fabric will provide a closed structure that covers all the foliage, and it will be made from bio-based polymers. 

“We’re not adding more plastic into the world,” he says.

Engineering a Fabric to Meet the Challenge

Farer, a professor of textile engineering, chemistry and science in the Wilson College of Textiles, and Whitehill, an assistant professor and Extension specialist in the College of Natural Resources, first started talking about collaborating on a deer browse solution last year.

Farer had shown a lightweight crop covering being tested at The Nonwovens Institute to N.C. PSI Executive Director Adrian Percy, who encouraged Farer to reach out to Whitehill.

Farer did, and as he and Whitehill talked, they realized that, with some tweaking, the fabric might be useful in protecting trees from deer. The two applied for, and recently won, a federally funded specialty crop block grant from the N.C. Department of Agriculture and Consumer Services to pursue an affordable nonwoven covering to protect trees during their first three years of life.

Unlike woven fabrics, nonwovens are made from fibers that are pressed or fused together. By varying the fiber type and altering how the material is made, manufacturers can tailor-make nonwovens to serve different purposes: Nonwoven diapers, for example, are made to be absorbent, while surgical masks are meant to be breathable.

Farer is aiming for a fabric that can be shaped into a cone, allowing farmers to easily place it over the tree, stake it down and then remove it when needed.

Ideally, the covering won’t have any negative effect on tree growth. That means it must let sunlight pass through and allow for heat and moisture exchange, especially during hot summer months.Not only that, the covering also has to be durable enough to endure harsh mountain wind, rain and snow.

Once the covering is developed, Whitehill’s lab will test hundreds of them on Fraser fir farms and research sites.

It took me all of 30 minutes or less to put the cones on the trees. … Definitely, the deer are not nibbling on those trees with the cones.

Cyndi Knudson is among those eager to see this project unfold. As an N.C. Cooperative Extension area farms specialist, director of research for the Real Christmas Tree Board and a self-described “micro-Christmas tree farmer,” she was so interested in the project that she asked Farer for some of his cone-shaped prototypes.

Farer gave Knudson about 10 to use on her farm in Lancaster County, Virginia, where she grows a total of around 100 Christmas trees, mainly as a hobby. 

So far, she’s been pleased with the fabric’s performance.

“It took me all of 30 minutes or less to put the cones on the trees,” she says. And while she thought the wind would blow them off, that hasn’t happened.

Moreover, Knudson feels confident the covers are doing their job. “Definitely, the deer are not nibbling on those trees with the cones.”

This post was originally published in Plant Sciences Initiative.