Bark

The bark is the outer part of a tree. Similar to human skin, it serves as a protective covering that shields the tree from injury and temperature extremes. The bark of a Douglas fir in British Columbia can be up to 30 centimetres in thickness.

The inner bark of a tree is soft and moist. Its main function is to produce the tree's annual rings. It conveys nutrients to the branches and trunk of the tree. Did you know that a tree can starve to death? It can if its bark is injured or cut down to the wood in a ring all around the trunk. This is called deadening or girdling.

Bark has many uses. In olden times, a chemical extracted from the bark of the hemlock and some oaks was used to tan leather. The inner bark of the hemlock was also used as a dye. The inner bark of the linden and elm was used to make rope, to weave baskets, and to cane chair bottoms.

Jacques Cartier was impressed with the medicinal properties of the bark and leaves of the Eastern white cedar. He named it "tree of life" in honor of the aboriginal chief who showed him how to cure his crew of scurvy (a disease caused by a lack of vitamin C) with a tea made from its bark.

Bruising the bark of the yellow birch produces the same odor as wintergreen. What do aspirin, yellow birch, and wintergreen have in common? They all contain a medicinal called methyl salicylate.

Dried bark can be combined with other materials and pressed into wood briquettes or pellets that are used as fuel. Industry can use them to save on transportation and storage costs.

Bark has a number of decorative and practical uses around the house, too. It helps cut down on weed growth in flower beds. Some house plants, such as orchids, actually grow better in bark than in soil.

Bark can be used to produce litter and even an absorbent material for industrial purposes. Researchers are now looking for agricultural applications of bark. When mixed with pork manure, it can be spread on fields as a fertilizer.

Trees give us a number of other useful products. Some involve a process called wood distillation. Such products include charcoal, wood alcohol, tar, and other chemicals. Two well-known wood distillates are methanol and ethanol, which are liquids that can be used as fuels.