Notholithocarpus Densiflorus
The tanoak is a large broadleaf tree that is part of the beech family (fagaceae) which may be confusing, considering that they have “oak” in their name. They are not true oaks, though they are closely related and have similar acorns to oak trees.
They are closely related to the northern temperate region of oaks, which are part of the quercus genus. They are sometimes called tanbark-oak as well, and they get these names from the rich tannin content that is present in their bark. Tanbark was traditionally used for tanning leather before modern synthetic tannins came around.
Tanoak trees are native to the western United States, specifically California, and Oregon. The largest recorded tanoak tree is 121 meters tall, and they have life expectancies of several centuries! They are a very important member of the mixed evergreen forest.
Curious about other types of trees? Check out what we learned about the Coastal Redwood Tree that commonly grows with the tanoak tree. Or, check out our huge series of 101 Types of Trees from around the world!
What do Tanoak Trees Look Like?
Root System
Tanoak trees grow very large, deep, and wide-spreading root systems. This makes them slightly different from true oak trees in that regard, whose roots only grow about 18 inches deep in the soil.
These deep root systems make the tanoak tree rather resistant to drought, though they prefer to grow in moist areas that experience a lot of precipitation.
Dimensions
Tanoaks are rather large trees, and can sometimes reach heights up to 40 meters tall. They tend to experience their greatest growth in the more coastal ranges of their growing regions. Trees in the upper category of height will usually have a trunk diameter ranging from 190 cm around, with smaller trees having trunk widths of 60 cm.
Growth Pattern
Trees usually experience different growth patterns that are entirely dependent on their growing regions. When a tanoak tree is growing in a dense forest where there is a lot of canopy competition, it will develop narrow crowns in order to fit inside the coveted canopy spots.
When a tanoak tree is growing in a more open area where there is not much canopy competition, they will extend the crown into a more rounded shape, since there is no need to conserve energy when they have full sun access.
Bark
The bark of a tanoak tree is a lovely light brown/gray color, and it grows in thin sheet-like plates with flattened ridges that are a slightly lighter version of the same color.
Foliage
Tanoaks are evergreen trees, meaning that they have leaves that persist all year long. However, they are not coniferous, so they do have leaves instead of needles. Tanoak leaves are alternately arranged on a leaf and are usually 7-15 cm long.
They have toothed margins and a hard texture that is similar to leather. They are a dull green color are covered in dense scruffy hairs that are an orange/brown color. These scruffy hairs will eventually wear away on the upper surface of the leaf but will stay on the underside. A tanoak leaf will remain on a tree for 3-4 years before it dies.
How do Tanoak Trees Reproduce?
Flowers
Tanoak trees are monoecious, meaning that both male flowers and female flowers occur on the same tree. Male flowers release pollen, and it is carried through the wind to female flowers, resulting in wind pollination.
Female flowers are borne in dense drooping clusters of yellow blossoms. A female flower can be found at the base of the male flower, which is found on the axils of the current year’s shoots.
Male flowers are borne individually and are also yellow blossoms. Whereas female blossoms are drooping, male blossoms stand erect and grow from the axils of the current year’s shoots.
Tanoak trees tend to bloom in the summer months, though if climate conditions are unusual they will sometimes flower in the spring or fall as well.
Germination
The seed production of the tanoak tree is very abundant. A tree will usually produce upwards of 110,000 seeds annually. Productive seed crops occur every 2 years, with less productive crops occurring in the years in between.
Germination occurs best under forest debris under full forest cover, which is rather unusual for germination, as seeds usually need warmth and sun exposure in order to grow.
Seeds
Seeds ripen in the second autumn after they were pollinated. A mature seed is in the form of an acorn. Tanoak acorns are 2-3 cm long, and 2 cm wide. They look very similar to the regular oak acorn.
This hard tanoak acorn nut is covered in a shell, quite similar to a hazelnut. The nut is capped by a cup that is rough in texture, with short spines covering the surface. Nuts are borne in clusters. The inner kernel of the acorn is very bitter and is inedible to people unless it is extensively leached.
However, squirrels, insects, birds, rodents, bears, raccoons, and deer all heavily forage for these tanoak acorns.
Sexual Maturity
Tanoak seedlings as young as 5 years old can produce seeds, though their most productive years occur between the ages of 30 and 40. These trees have very productive crops every 2 years, with slightly less productive crops the years in between.
Where do Tanoak Trees Grow?
The tanoak tree is a native tree to the west coast of the United States. They are usually found growing alongside the Coastal Douglas Fir, as well as the Coast Redwood.
These trees grow prominently in northern California and southern Oregon, with impressive groves occurring in Santa Barbara, the Siskiyou Mountains, and in many different coastal regions. They will grow from sea level up to 5000 meters in elevation and occur most commonly in the redwood forest as a pacific coast hardwood tree.
What are the Growing Conditions of Tanoak Trees?
Soil
Tanoak trees can grow in many soil types, though they do have their preferences. They tend to grow best in very deep soils. They can be sandy, or gravelly, or loamy soils, though they must be well drained.
These trees are very commonly found in shallow stony soils, on northern slopes. They cannot tolerate flooding, though they do perform quite well in drought conditions.
Sun Exposure
Tanoak trees are very shade tolerant, which is convenient since they grow amidst redwood trees and Douglas fir trees which can be over double the height of tanoak trees. Not only are the trees tolerant to shade, but their seedlings also germinate most successfully in shady conditions.
Water Level
The main requirement for tanoak trees is living in areas with plenty of moisture. They prefer to exist in heavy humidity, and in regions that experience a minimum of 40 inches of precipitation per year.
Temperature
The tanoak tree will only grow in areas that have a mean winter temperature of 42 degrees Fahrenheit, and a mean summer temperature of 74 degrees Fahrenheit.
How are Tanoak Trees Used?
Wood
Tanoak wood greatly resembles that of true oak wood. It is heavy, hard, with an even texture but little apparent grain. The wood is a light red/brown color when it is first cut, but eventually ages into a darker shade of that.
Tanoak wood is most commonly used for truck bedding, ties, veneer, pulpwood, firewood, furniture manufacturing, mine timbers, and paneling.
Mulch made from tanoak wood and leaves is also said to be a natural grub and slug repellent and comes in handy to landscapers.
Wildlife
The acorns of the tanoak tree are a very important source of food for various animal species. Birds, deer, bears, raccoons, rodents, chipmunks, and squirrels all forage heavily on these acorns.
These trees are also an important habitat for various animals. They provide thermal cover and refuge for endangered animals, like flying squirrels, northern spotted owls, and dusky-footed wood rats.
Ethnobotanics
Certain First Nations communities have traditionally used tanoak acorns for food. It is said that these acorns are preferred to Quercus acorns, as the high tannin content of tanoak acorns store for longer.
Acorns are processed and used to make meals, bread, pancakes, biscuits, and cakes. They can also be roasted and eaten as is, or roasted seeds can be used as a substitute for coffee.
FAQs
Does tanoak wood make for good firewood?
Because of the heaviness and hardwood qualities of tanoak wood, it makes for good firewood. Not only because it burns slowly and has a high heat capacity, but because it isn’t greatly valued in the lumber industry, and burning it isn’t considered as being wasteful.
Is tanoak a hardwood?
Yes, tanoak wood is considered a relative hardwood.
How deep do tanoak roots go?
Tanoak trees grow very large, deep, and wide-spreading root systems. This makes them slightly different from true oak trees in that regard, whose roots only grow about 18 inches deep in the soil.
These deep root systems make the tanoak tree rather resistant to drought, though they prefer to grow in moist areas that experience a lot of precipitation.
How tanoak roots invasive?
Tanoak roots aren’t considered as being invasive because they tend to grow deep in the earth in a rather regular pattern, therefore not interfering with plumbing or other types of infrastructure.
What is the life expectancy of the tanoak tree?
The average life expectancy of the tanoak tree is around 400 years, with ages occurring regularly between 250 and over 500.
How fast do tanoak trees grow?
Tanoak trees are quite fast-growing and can grow anywhere from 12 to 24 inches per year.
How tall do tanoak trees get?
Tanoaks are rather large trees, and can sometimes reach heights up to 40 meters tall. They tend to experience their greatest growth in the more coastal ranges of their growing regions. Trees in the upper category of height will usually have a trunk diameter ranging from 190 cm around, with smaller trees having trunk widths of 60 cm.
What animals eat tanoak acorns?
The acorns of the tanoak tree are a very important source of food for various animal species. Birds, deer, bears, raccoons, rodents, chipmunks, and squirrels all forage heavily on these acorns.
Are tanoak trees affected by sudden oak death?
The tanoak tree is, unfortunately, one of the most vulnerable tree species to sudden oak death, which is caused by the fungus Phytophthora ramorum. This is a water mold pathogen that is also responsible for leaf blight and numerous cankers diseases that ail various tree species.
Can you eat tanoak acorns?
It is very important to properly process tanoak acorns, as the kernels are incredibly bitter when they are untreated.
Certain First Nations communities have traditionally used tanoak acorns for food. It is said that these acorns are preferred to Quercus acorns, as the high tannin content of tanoak acorns store for longer.
Acorns are processed and used to make meals, bread, pancakes, biscuits, and cakes. They can also be roasted and eaten as is, or roasted seeds can be used as a substitute for coffee.
Why is it called a tanoak tree?
Tanoaks are closely related to the northern temperate region of oaks, which are part of the Quercus genus. They are sometimes called tanbark-oak as well, and they get these names from the rich tannin content that is present in their bark. Tanbark was traditionally used for tanning leather before modern synthetic tannins came around.
Are tanoak trees oak trees?
Though tanoak trees are related to the true oak tree and are relatively similar in appearance, they are not part of the genus Quercus but instead are part of the beech family, which is the genus Fagaceae.
What family are tanoak trees part of?
Tanoak trees are part of the beech botanical family, which is the genus Fagaceae.
Are tanoaks rich in tannins?
Tanoak trees are an organism that is very rich in tannins. The tannins are present in the bark, foliage, and acorns of the tree.
Are tanoak trees shade tolerant?
Tanoak trees are very shade tolerant, which is convenient since they grow amidst redwood trees and Douglas fir trees which can be over double the height of tanoak trees. Not only are the trees tolerant to shade, but their seedlings also germinate most successfully in shady conditions.
Can tanoak trees grow in cold weather?
The tanoak tree will only grow in areas that have a mean winter temperature of 42 degrees Fahrenheit, and a mean summer temperature of 74 degrees Fahrenheit.
Is there a Tanoak Tree book?
The plant pathologist and botanist, Frederica Bowcutt, wrote a book about the tanoak tree. Here we quote the Google Books description of the book “The Tanoak” by Frederica Bowcutt that discusses the environmental history of the tree:
“Tanoak (Notholithocarpus densiflorus) is a resilient and common hardwood tree native to California and southwestern Oregon. People’s radically different perceptions of it have ranged from treasured food plants to cash crops to trash trees. Having studied the patterns of tanoak use and abuse for nearly twenty years, botanist Frederica Bowcutt uncovers a complex history of cultural, sociopolitical, and economic factors affecting the tree’s fate.
Still valued by indigenous communities for its nutritious acorn nut, the tree has also been a source of raw resources for a variety of industries since the white settlement of western North America. Despite ongoing protests, tanoaks are now commonly killed with herbicides in industrial forests in favor of more commercially valuable coast redwood and Douglas-fir.
As one nontoxic alternative, many foresters and communities promote locally controlled, third-party certified sustainable hardwood production using tanoak, which doesn’t depend on clearcutting and herbicide use.
Today tanoaks are experiencing massive die-offs due to sudden oak death, an introduced disease. Bowcutt examines the complex set of factors that set the stage for the tree’s current ecological crisis.
The end of the book focuses on hopeful changes including the reintroduction of low-intensity burning to reduce conifer competition for tanoaks, emerging disease resistance in some trees, and new partnerships among tanoak defenders, including botanists, foresters, Native Americans, and plant pathologists.”
