The US market share of real Christmas trees has shrunk to less than 20% of that held by artificial Christmas trees. “Messiness” resulting from needle drop is a frequent criticism of real trees. Early harvest, storage, and distribution of wholesale Christmas trees can contribute to poor performance. Identification of treatments to improve Christmas tree needle retention during farm storage is a critical research need of real tree growers. Among plant growth regulator compounds, those that block or otherwise interfere with ethylene influence on needle abscission such as 1-MCP are of particular interest.

1-MCP treatments were made to branches and whole Fraser fir Christmas trees in several postharvest needle retention studies in North Carolina spanning 2010 through 2018. A pattern of slightly better needle retention associated with 1-MCP was observed across different years, experimental designs, and storage conditions. In 2019, dramatically improved needle retention occurred to branches of poor-performing Fraser fir clones treated with 1-MCP. However, this occurred after branches were unintentionally left in their dark 1-MCP gas chamber an extra two weeks.

Studies conducted in 2020 and 2021 sought to repeat 2019 conditions and results. Three rates of 1-MCP gas chamber and spray-applied treatments were tested in 2020 across different storage durations using clones with known needle retention performance. After mixed results in 2020, a full matrix of 1MCP rates and dark storage durations were implemented in 2021 using six clones selected for differing needle retention performance. As in earlier pre-2019 studies, 1-MCP treatments revealed a slight positive rate response in needle retention. However, durations of dark chamber storage without 1-MCP (2, 7, and 14 days) revealed a more significant contribution to differences in needle retention. Results have implications for both future postharvest research and farm storage of Fraser fir Christmas trees.