How climate change is reshaping the Christmas tree

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Nothing is more emblematic of the Christmas season than a twinkling, bejeweled evergreen tree surrounded with presents.

But as climate change causes extended periods of drought and warm temperatures, even hardy Christmas trees are struggling to thrive. This has spurred some Santa Cruz-area Christmas tree farmers to become more innovative in their approach to growing the trees.

Located midway between Santa Cruz and Monterey near Elkhorn Slough, Church Christmas Trees Farms is a family-run, cut-your-own-tree farm that has been in operation for more than half a century. But the landscape of trees has been increasingly affected by droughts and hot temperatures that have plagued central California.

The trees just “haven’t looked as good,” notes Glenn Church, owner of Church Christmas Tree Farms, who says he’s had to cut back “dramatically” on the number of trees he’s able to grow.

Hot summer rays have singed trees on their south-facing sides, causing Church to have to limit new trees to shadier areas of the farm. Periods of drought make it difficult for young trees to establish their roots, further challenging the tree farm.

Christmas tree farms, unlike much other agriculture, typically rely on rainfall rather than irrigation. “So when there are long periods of dry, hot summers, there is a lot of mortality,” explains Chal Landgren, a Christmas tree specialist at Oregon State University. Trees are particularly vulnerable in the first year or two of their life.

In order to grow and thrive, trees rely on photosynthesis to make their sugary food. Water and carbon dioxide (CO2) from the air are two of the key ingredients in this process. Water shortages lead trees to close pores on their leaves — needles on a fir tree are indeed leaves — to prevent any water loss. Pore closure limits a tree’s ability to take in CO2, which in turn makes it difficult for photosynthesis to take place and for sugars to be produced.

“Trees, including Christmas trees, are facing the situation where at times photosynthesis is choked off because there’s not enough water to open those pores,” says Michael Loik, a tree physiologist at UC Santa Cruz.

Heat can create a similar problem, says Loik: “Rising temperatures, even without a change in rainfall, cause enhanced evaporation.” This enhanced evaporation can similarly lead trees to close their pores, disrupting photosynthesis.

The first one to two years of life is when it is most necessary for trees to take root. One solution Church has been using on his tree farm is a process called “stump culture.”

“Basically if you cut a tree and there’s a little bit of green left on it, it’ll grow up into another tree,” explains Church. Since the roots are already established, the tree is much more drought resistant.

It is difficult to predict which trees will grow best as the climate continues to change. Loik says tree farmers are “betting on the future and making an investment that doesn’t pay off for several years later.” As a result, it can be challenging to figure out what works for keeping trees healthy. One approach might be to “plant a bunch of different species to make sure that at least some of them do OK five or 10 years down the road.”

Trees on Church’s farm typically take four to 12 years for the tree to reach maturity, depending on the species; Church says he currently has about 30 different species. The farm’s most popular type is the Monterey pine, but the species has been affected by disease, Church adds. Cedar trees as well as Douglas and white firs are also popular, but these species are slower-growing.

Church, like many other tree farmers, is experimenting with growing more drought-resistant species like cypresses. Specifically, Church has been growing the Arizona cypress as well as the Leyland cypress — the latter of which is popular because it doesn’t produce cones or pollen and is therefore great for people who have allergies. Cypresses also grow faster than more classic trees like the Douglas and white firs — an added bonus.

Unlike traditional Christmas trees, however, cypresses tend to grow into the shape of a bush and need to be sheared into a classic Christmas tree shape — a task Church takes on prior to selling them.

The trees that do well might not be what people typically think of as a Christmas tree — a cypress instead of classic Douglas fir, for example. This isn’t necessarily a problem, though. “In the past, people had a view of what a traditional Christmas tree was, and that’s what they wanted to get,” Church explains. “Now they’re willing to buy just about anything that will fit as a Christmas tree. It’s more of the adventure that they’re going for.”