The National Wildlife Federation, the Arbor Day Foundation and the National Christmas Tree Association are good resources for information about Douglas fir trees. In addition, several universities, including Oregon State and San Diego State, are sources of general and scientific information about the trees.
Arborday.org and NWF.org offer historical and scientific information about Douglas fir trees ranging from descriptions of the needles to the origin of the name. They describe growth rates and environmental, sun and soil preferences. Realchristmastrees.org, the website of the National Christmas Tree Association, is another source of general information, including propagation, types of seeds and uses.
Douglas fir is a genus that includes six different species of trees. These trees grow in California, Oregon, Washington, parts of the Rockies and Alaska. They are one of the most popular types of Christmas trees.