Alder Trees

Published January 31, 2019
Alder trees

Fans of fairy tales are likely very familiar with the Alder tree. The popular genus of Alnus belongs to the birch family and is best known for its light and delicate features. What's more, the tree is a haven for woodland creatures commonly associated with fables and folktales. However, in order for Alders to live happily ever after on your property there are some key factors you should know about the tree.

Appearance of the Tree

While the Alder derives from a family of flowering plants, the tree is probably best known for the purple sheen that appears during the spring. The fast-growing deciduous trees thrive along streams and rivers where they reach an average height of 40 feet.

Other notable characteristics of the Alder include:

  • Bark: Thin and grey
Alder tree trunk
  • Leaves: Small and round with serrated edges
Alder green leaves
  • Flowers: Long light-green male catkins appear before the leaves sprout, while female catkins are purple, ball-shaped and woody
Catkins of Alder
  • Fruit: Small brown cones containing dozens of tiny seeds that are spread by the wind.

Another distinctive characteristic of the Alder is the lichen which covers nearly all of its bark. The clingy lichen creates an intricate pattern of white and grey markings with small tinges of pale pink. The mosaic patterns are similar to hieroglyphs and make the tree look more like a birch when completely covered with the fruiting fungus.

Alder trunk wood texture

Alder Tree Types

Alders need very specific growing conditions in order to grow and prosper. Consequently, the best-known species tend to congregate in select regions of the world. They include:

  • Red Alder: The red Alder is exclusive to the northwest portion of the United States, namely Alaska, California, and Idaho. In addition, you can find some red Alders in Hawaii where they thrive in wet areas. The medium-sized trees can reach heights of 45 feet and can live up to 100 years. The thin outer bark is grey and typically covered with lichen while its inner bark is reddish-brown.
Forest of Red Alders
  • Black Alder: Also known as the European Alder, this particular tree is popular among landscapers. The rapidly growing tree lives about 20 years, reaches heights up to 70 feet and is an excellent choice as a windbreaker.
  • Grey Alder: This Alder is smaller than its cousins, reaching a maximum height of just 15 feet. The tree is treasured for its ability to grow in infertile soil. In addition to being hard to kill, the Grey Alder is known for its beauty. In the spring the Grey Alder is covered with drooping seed-containing green and purple catkins.

The Many Looks of the Alder Tree

Alder forest during summer
Healthy alder tree
Alder tree roots
Alder tree roots
Alder tree cones and caskins
Alder tree cones and caskins
Black alder leaves in spring
Alder leaves in spring
Alder tree in the summer
Alder tree in the summer
Alder tree branches in winter
Alder tree branches in winter
Black alder tree
Black alder tree
Alder wood texture
Alder wood
Alder tree in swamp
Alder tree in swamp

Where the Alder Grows

The Alder tree prefers damp conditions and thrives in swamps and marshlands. While Alders don't necessarily need to be planted near rivers or streams, they will suffer in drought conditions unless their roots are submerged in water.

  • In Europe, Alders are bountiful in:
  • The Great Plain states, including
  • Kansas and Nebraska
  • The Western portion of the U.S.,
  • including California and Oregon
  • Arizona
  • New Mexico
  • Canada
  • Europe
  • Parts of the Middle East and Eastern Africa

In the United States, Alders can be found in northern California, isolated parts of Idaho, Hawaii's tropical rainforests and Alaska.

Popular Uses

Alder trees are attractive and functional with numerous uses, including:

  • Wood: Used for furniture, cabinets and smoking salmon.
  • Food: Indian tribes used to scrape inner bark of tree and mix it in recipes, such as cakes and salads.
  • Dye: Red Alder are cut and boiled to create dyes for clothes.
  • Medicine: Oil from the tree's bark is used to treat diarrhea, nausea and muscle aches. Also, heated Alder leaves help with skin diseases.
  • Nutrition: Alders add nitrogen to the soil which helps other plants grow. The trees are often planted in places where logging has occurred to provide nitrogen and other nutrients to young seedlings.
  • Decoration: The brown cone-like fruit from Alder trees are often used in floral arrangements, especially during the fall and winter months.

Interesting Facts

Alders hold a prominent place in history having been associated with the Welsh goddess Bran who carries Alder branches in her arms. Meanwhile, in Ireland, Alders are associated with death, as the tree's branches were often used to measure graves. In other parts of the world, Alder ashes are used to cure fevers. Individuals believe if they consume the ashes, and then vomit them up; the cause of the fever will exit their bodies as well.

Alder Diseases

Since Alder tree roots contain such high levels of nitrogen, they are not susceptible to as many diseases as other foliage. However, this doesn't mean the tree is indestructible. Alders are vulnerable to Phytophthora disease and a fungal disease called Artist's Bracket. The former stunts the tree's leaves and causes black, tar-like spots on the tree's dying bark. Meanwhile, Artist's Bracket can cause root rot, butt rot, and white rot. The tree can also be attacked by the leaf beetle which eats large holes in the leaves.

Alder Care

Caring for Alders is not complicated provided you are able to provide the tree with adequate water. Alders need moisture to survive. As long as you keep the roots damp and the canopy is not starved of sunlight, the Alder should thrive.

Other tips to keep your Alder in tip-top condition include:

  • Pruning: Alders need to be pruned regularly. If you neglect to trim the tree seasonally it will turn into a spreading thicket of stems.
  • Fertilizing: Since the Alder produces its own nitrogen, you don't need to ever fertilize it.
  • Sunlight: Alders prefer full sunlight, though they will tolerate partial shade.

Allergy-Sufferers Avoid

Alder flowers blossom in the early spring. Despite their beauty, the blooms contain a large amount of pollen which can cause severe reactions in people with allergies. If you suffer from pollen allergies, Alder trees should not be a part of your landscape.

Alder Trees Make a Great Landscaping Choice

The many looks of the Alder tree makes it a desirable landscaping choice. If you want a fast growing tree, the Alder won't disappoint.

Alder Trees