Picea sitchensis

The Sitka spruce, known scientifically as *Picea sitchensis*, is a massive coniferous evergreen tree.

It holds the title of the largest spruce species in the world. It is also the fifth-largest conifer on Earth, following the giant sequoia, coast redwood, kauri, and western redcedar. This tree is an incredible giant of the forest. It is one of only three tree species documented to exceed 90 meters in height. In fact, some individual trees reach 100.2 meters, or 329 feet. This makes it the third-tallest tree species on the planet.

To understand how this tree grows, we must look at its unique biology. The Sitka spruce thrives in extremely wet and poorly drained soils. Because the ground is so saturated, the tree cannot grow deep roots. Instead, it develops a shallow root system with long lateral roots. These roots spread out sideways to find stability. However, this shallow structure makes the tree susceptible to wind throw, where wind knocks the tree over. The tree also features specific foliage. The leaves are stiff, sharp, and needle-like, measuring 15 to 25 millimeters long. These needles are dark glaucous blue-green on top. They have two or three thin lines of stomata, which are tiny pores for breathing. The underside is blue-white with two dense bands of stomata.

There are several distinct parts and stages to the Sitka spruce's life and appearance. As the tree matures, its crown changes shape. Young trees have a broad conic shape, like a cone. Older trees develop a more cylindric, or cylinder-like, shape. The bark is thin and scaly, flaking off in small, circular plates. The inner bark has a reddish-brown color. The tree also produces cones that are pendulous and slender. These cones are long and broad when closed. They open to become broad once they mature. The seeds inside are black and long. They feature a slender, pale brown wing that helps them travel.

History and discovery have shaped our understanding of this species. The name comes from the community of Sitka in southeast Alaska. In 1831, David Douglas introduced the Sitka spruce to Europe. Since then, it has become a major part of many forests. In Great Britain, it makes up 25% of the forest cover. In Ireland, it accounts for 52% of the forest cover. In Norway, the tree was introduced in the early 1900s. It grows 25% to 100% faster there than the native Norway spruce. Because it grows so aggressively, it is now considered an invasive species in Norway.

Specific measurements show just how enormous these trees can be. The Queets Spruce, located near the Queets River in Olympic National Park, is the largest in the world. It has a trunk volume of 1,491 cubic meters and a height of 94 meters. Its diameter at breast height is 5.4 meters. Another massive tree, the Carmanah Giant, is the tallest in Canada at 95 meters. While these trees are huge, they are not always ancient. The Sitka spruce grows very rapidly in favorable conditions. The Queets Spruce is estimated to be only 350 to 450 years old. However, it adds more than one cubic meter of wood every single year. The oldest known individual is just under 600 years old.

These trees provide vital support to many different ecosystems. They offer critical habitat for mammals, birds, reptiles, and amphibians. For example, bald eagles and peregrine falcons use them for nesting. In Alaska and British Columbia, the needles are a major food source. They make up 90% of the winter diet for blue grouse. Sitka deer also rely on old-growth forests for winter habitat. The thick foliage helps hold up fallen snow. This allows animals to move more easily through the understory. Even the fungi, such as *Helocarpon lesdainii*, find homes on these trees.

Finally, the Sitka spruce has important connections to human technology and culture. The wood has a high strength-to-weight ratio. This makes it an excellent conductor of sound. Because of this, it is used to make musical instruments like pianos, harps, violins, and guitars. It is also used for sailboat spars and aircraft wing spars. The Wright brothers used Sitka spruce to build the Flyer. During World War II, the British Mosquito aircraft used it as a substitute for aluminum. Native Americans also used the tree for many things. They used the root bark for basket-weaving and rain hats. They even used the resin as glue and for waterproofing.