The alder tree can be found growing along the west coast of North America, most of Europe and in British Columbia. These trees are commonly found in moist areas, growing near or next to water.
Alders can range from a large tree that grows from 40 to 80 feet tall or a small shrub that remains under 25 inches. Over 80 different species of the alder are native to North America alone, including the red alder, white, Sitka and the thin-leaf alder. The red leaf alder is abundant in Oregon and is characterized by its beautiful red wood and curled leaves.
Alder trees are deciduous with only a few exceptions. They all feature simple, serrated leaves and the flowers appear as elongated male catkins. Some species of the trees are considered weeds in parts of New Zealand, although the leaves and the catkins are often used as food by moths and butterflies. The catkins are also used to smoke various food items including salmon, and alder bark is known for its use as an anti-inflammatory salicin.
These trees release good amounts of nitrogen into the soils, which allow them to form an important symbiotic relationship with many bacterium. These bacterium grow in the root nodules, are as large as the human fist and are light brown in color. The result of this mutual relationship is extremely fertile solid in the area where the alders grow.