Forty-five percent of Washington state is covered with trees, and six percent of that area--or 3 million acres--consists of old growth forest, according to the Visit Old Growth Forests website. Some of the nation's largest trees are in Washington old-growth forests.
American Forests, a nonprofit organization, maintains the National Register of Big Trees, which ranks trees by trunk circumference, height and average crown spread. Of the 733 registered trees, five of the top 20 are located in Washington (as of October 2010).
Western Red Cedar
At fourth place in the American Forests' National Register of Big Trees is a Western Red Cedar, or Thuja plicata. With a circumference of 761 inches, a height of 159 feet and a spread of 45 feet, this huge tree is located in western Washington's Olympic National Park. The tree is on the north shore of Lake Quinalt. In the wild, Western Red Cedars generally reach a height of 130 to 200 feet, with an average spread of 15 to 20 feet.
Coming in fifth in the National Register is a Sitka Spruce, or Picea sitchensis. The tree is 191 feet tall tall, has a 668-inch circumference and a 96-foot spread. This large spruce tree is also located near Lake Quinalt in the Olympic National Park. Generally, Sitka Spruce reach an average height o 125 to 180 feet with a spread of three to five feet.
Coast Douglas Fir
A Coast Douglas Fir, or Pseudotsuga menziesii, ranks number six on the National Register. With a circumference of 505 inches, a height of 281 feet and a spread of 71 feet, this tree is significantly larger than the average Douglas Fir. According to Tree Help, this species generally reaches an average height of 40 to 80 feet with a spread of 12 to 20 feet. The champion Coast Douglas Fir is located within Olympic National Forest near the Queets River Valley, according to the Gymnosperm Database.
Coming in 17th on the National Register of Big Trees is a Noble Fir, or Abies procera. This tree reaches a height of 227 feet, has a 359-inch circumference and a 41-foot spread. Noble Firs generally reach heights of 132 to 175 feet, with a 45- to 60-inch circumference, according to the USDA Forest Service. This large Noble Fir is located in the Gifford Pinchot National Forest in southwestern Washington.
A 126-foot-tall Alaska Cedar, or Cupressus nootkatensis, ranks 20th on the National Registry of Big Trees. With a circumference of 451 inches and a spread of 27 feet, this tree is much larger than most Alaska Cedars, which average a height of 75 to 100 feet with a 24- to 36-inch circumference, according to the USDA Forest Service. This Alaska Cedar is located in Olympic National Park, about one mile east of Three Lakes.