Climate Change Shapes the US Christmas Tree Industry: Adaptation, Mulching, and New Fir Species

Overview

In this Science Quickly episode, host Kendra Pierre-Louis speaks with Priya Rajarau of Oregon State University about how climate change is reshaping the modern Christmas tree industry. The discussion covers what trees are grown as real Christmas trees, how they are cultivated, and the differences between farmed trees and their forest counterparts. The episode also examines pressures from warming temperatures and reduced precipitation, and how growers are experimenting with practices to safeguard seedlings and production.

Key Takeaways

US production reaches tens of millions of trees annually, with Oregon, North Carolina, Washington, and Michigan as major players. Drought and heat stress threaten seedling establishment, prompting mulching and other management trials. Introducing European-origin Norman fir and Turkish fir offers resilience to temperature and pests, helping maintain supply. Consumer choices and price, including synthetic trees, influence the market, but growers are actively working to keep real trees available.

Introduction

In this Scientific American Science Quickly episode, Kendra Pierre-Louis engages Priya Rajarau, an assistant professor and Christmas tree extension specialist at Oregon State University, to discuss how climate change is affecting the Christmas tree industry in the United States. The conversation outlines the cultural significance of evergreens and describes how Christmas trees are farmed, including how pruning and cultivation create the classic triangular shape that shoppers expect.

What Christmas Trees Are and How They Grow

Most Christmas trees are firs or other evergreens, valued for keeping needles through the season. Although many trees come from forests, commercial Christmas trees are a farmed crop with a 5–10 year rotation, depending on species. Growers prune and culture trees to maximize fullness and hide stems, much like other vegetable crops. The industry is a substantial agricultural sector, with 14 million trees produced in the US as of a 2022 survey, concentrated in Oregon, North Carolina, Washington, and Michigan.

Climate Pressures and Seedling Establishment

Rajarau highlights how rising temperatures and decreased precipitation are challenging seedling survival. In the Pacific Northwest, periods with little or no rain—recently extending to about 100 days—stress newly transplanted seedlings during the crucial establishment year. The first year is pivotal for long-term production because each harvested tree is accompanied by several new seedlings in the ground. A field study at OSU tests mulch as a strategy to conserve soil moisture and reduce soil temperature, aiming to improve seedling survival during hotter, drier seasons. A recurring concern for growers is mulch quality, potential disease transmission from mulch sources, and cost considerations.

"the changing temperatures and lesser precipitation" - Priya Rajarau, assistant professor, Oregon State University

Mulching and Root Management

Mulching emerges as a practical approach to retaining soil moisture, with wood mulch showing promise in improving seedling survival and lowering soil temperatures. Rajarau notes that polymers and root dips have been explored, but traditional mulch remains the hero in boosting establishment success. The team is evaluating various mulch materials, including sawdust, compost, and hazelnut shells from Oregon's hazelnut industry, to identify affordable and effective options while monitoring potential nutrient competition with seedlings.

Diversifying Species and Genetics

To cope with climate stress, researchers from OSU and North Carolina State University, with support from other institutions, have pursued seed collection from trees with favorable traits in Georgia and Turkey. Norman fir and Turkish fir emerged as promising options, performing better under warmer, drier conditions and showing resilience to pests compared to some native species. Seed orchards are being developed to propagate these genetics, which may help stabilize supply and diversify risk as local climates shift. Noble fir, a native species, has shown greater temperature sensitivity, reinforcing the case for exploring European-origin alternatives.

Supply, Demand, and Outlook

Despite climate pressures, growers are actively working to maintain live-tree availability for consumers. There is a noted decrease in total Christmas tree acres in production, but prices and consumer preferences will influence adoption of new practices and species. Artificial trees remain a factor in the market, balancing convenience and cost with the enduring appeal of real trees. The episode concludes with an optimistic note about continued supply and ongoing research to adapt to changing climate patterns.

"We usually have more trees than we have consumers" - Kendra Pierre-Louis, host