Colorants

Today, I’d like to address an issue that recently came up about Christmas Trees which can cause some people to have misunderstandings.

A recent article in the Chicago Tribune talked about how most people don’t know a “secret” about Christmas Trees. The “secret” described was that trees are “spray painted green.” Well, sometimes the news media just simply gets it wrong, or at the very least incomplete. Here’s the real story about this “secret.”

In colder climates, many evergreen species of trees stop conducting photosynthesis in late summer as they prepare for a dormancy stage. This cessation of photosynthesis leaves less chlorophyll in the needles. Chlorophyll is the chemical which makes needles (and leaves of deciduous trees) green. With the absence of chlorophyll, the needles are subject to fading and “bleaching out” by the ultraviolet light from the sun, particularly the pines. This is a natural process but can result in Christmas Trees which appear “yellow” from the faded color. Nobody wants a tree like that.

Growers can’t stop a tree from going dormant each winter nor can they force a tree to keep producing chlorophyll. However, they can do something which can protect the tree from ultraviolet light. To do this, a water-based colorant is applied to the trees by a spraying machine in late summer, usually August or September. The colorant blocks ultraviolet light from penetrating the needles and causing them to fade in color. Since the colorant is water-based, it is washed off by rain during the Autumn months, but by November the sun is far enough to the southern horizon as to not cause fading or “bleaching.” By the time a Christmas Tree is harvested around Thanksgiving and put up, the colorant is gone.

Trees that are already yellow-ish are not “spray painted green” as described in the article. That kind of incomplete explanation was just silly. It would be analogous to applying sunscreen to a person at 5 p.m. when they have been out in the sun all day long already.