Burl – Everything You Need To Know

Burl growth is a fascinating natural occurrence that happens to trees. It’s a mass of deformed tree cells that wrap around the back of a tree trunk, usually in a flattened hemispherical outgrowth. 

While it may not be particularly pretty at first glance, burl is valued highly by woodworkers for its unique and beautiful grain patterns.

Burl growth can happen for a variety of reasons, but it’s most often caused by stress. Early growth is small but grows large in size over time, and it usually has a spherical shape. 

Sometimes referred to as “Burrs,” burl growth is a strange collection of tree cell formations that can be found on a variety of tree species. In this article, we’ll explore all there is to know about burl growth, including its causes, characteristics, and uses. 

So, let’s dive in and become experts on this fascinating natural occurrence!

woodworking projects using burl

Table of Contents

What Is A Burl?

Burls are a peculiar-looking growth on a tree with the wood grain developing in an unusual configuration. Burls are frequently found on the tree’s trunk or closer to the roots.

Shape & Size 

They usually have a spherical shape and are wrapped around in the bark of different species of the tree. It might not be the most pleasing thing to look at but owing to the beautiful patterns on them, burls are valued highly by woodworkers.

In some regions, burls are also referred to as ‘burrs’. In their initial growing days, burls appear to be quite small. With time, they grow very large in size.

Burls, for example, can measure up to three meters in length. Some of them are so big that you’ll be astonished. What Does Science Say?

What the experts say

Burls, according to experts, is caused by the early development of trees. However, scientists have yet to determine what causes burls to form. There are a number of hypotheses going around, but none has been proved through any scientific evidence or proof.

A large number of scientists believe that burls start forming when the tree suffers from some kind of trauma. Some of the burls are a result of a fungus attack or an insect infestation. 

This theory is based on the fact that burls are often spotted growing on trees that are infested by insects or fungi.

Environmental theories 

Another scientific theory states that trees start producing burls owing to different environmental factors like air pollution or some minerals that are found within the soil. 

Scientists who back this theory say that burls often form on trees that grow in areas where the pollution levels are very high or weather conditions are erratic.

The scientific community hasn’t been able to agree on any one theory. Many scientists have carried out several experiments and tried growing burls in a scientifically controlled environment but have not achieved any success. 

burls form

Where To Find a Burl?

You don’t have to visit a forest to spot a burl growing on a tree. Visit a wooded area where trees are often overgrown.

Burls may be found on trees that grow near to water or in damp locations. Fungal growth is promoted by these regions, so you’re more likely to find burls on trees there.

burl found in wooded areas

What Are The Characteristics Of A Burl?

No Sapwood

Burl grows more slowly than other woods because it is so porous, and no amount of sapwood remains in it when it becomes old. This is one of the reasons why it appears unappealing to the eye. Another reason why burl is prized so much is that it lacks sapwood.

Grain Pattern

Burls are known for having distinctive grain patterns. These patterns tend to be very dark and make burls look very interesting. While these patterns appear organically, they could also emerge as a result of the wood being submerged in water for a prolonged period of time.


Burls are valuable because they are highly durable. Furniture made of burl wood lasts for decades. You will often come across furniture that is made of burl wood and is passed across different generations.

entire tree

What Are The Different Types of Burls?

Burls can be found growing in a variety of wood species. They can also be seen in different shapes and sizes. One of the most common forms of burl wood happens to be burl maple tree

What makes it unique is the fact that every piece of it looks different from the others. Some of the other popular types of burl wood include burl walnut, burl redwood tree and burl oak.

Walnut Burl Wood

A skilled woodworking carpenter would understand the value of walnut burl wood, which is usually quite pricey. Walnut burl wood is also used in the manufacture of automobile interiors.

Redwood Burl Wood

The name of this burl wood tells you exactly what you should expect out of it. While deep-colored redwood burl wood is quite common, you might also come across another variant that appears to be slightly pale.

Oak Burl Wood

Oakwood is characterized by the presence of very small burls. The valuation of timber with a large-eyed burl tends to be very high. Oak burl wood is quite expensive and they either have a golden yellow tint or are brown-colored.

Maple Burl Wood

In the commercial market, maple burl wood is widely sought after. They are used for a variety of purposes and are not very expensive. Cream, orange, red and tan are some of the colors the Maple burl wood is available in.

Birch Burl Wood

Birch trees are largely found in the forests of Alaska. These woods are expensive and when burl starts growing on these trees, their value increases exponentially. Birch lumber and burl wood are extensively used in making decorative pieces.

Cherry Burl Wood

Cherry burl wood is known for being extremely tough and durable. While it is used for making furniture, people also use it for different domestic purposes. The color of this burl is quite unique.

protected redwood forests

Where does the name come from?

The name Thuya Burl comes from the ancient Greeks, who called it thuya, which means “sacrifice plant.” They burned oil distilled from it as incense in their religious rituals, hence its Greek name. It is still used by some churches and has medicinal applications such as sandarac oil.

The History

The Burls are as lovely as they are fragrant, and the Greeks and Romans fought over furniture made from them. Thuya trees, along with cedars and oaks, once covered much of the Atlas Mountains in Algeria and Morocco, but today most areas have been treeless for hundreds of years owing to excessive harvesting.

The Consistency

The density, hardness, and oil content of Thuya burl are all very high. It is brittle, though it is quite firm and dense. Its color ranges from a rich, lustrous golden brown to nearly black.

The Appearance

The eyes are perfectly spherical, with a few burls scattered about them like the figure in bird’s-eye maple, and others grouped as islands. It is an exquisite wood that is currently used for inlays, small boxes, turnery, and precious objects.

Thuya burl


Burl tree growth can happen for a variety of reasons, but it’s most often caused by stress. Early growth is small but grows large in size over time, and it usually has a spherical shape. Sometimes referred to as “Burrs,” burl growth is a strange collection of tree cell formations that can be found on a variety of tree species. In this article, we’ll explore all there is to know about burl growth, including its causes, characteristics, and uses. So, let’s dive in and become experts on this fascinating natural occurrence!

People Also Ask

How valuable is a burl?

Burls, particularly layered burls, are not very valuable. A larger eyed burl in excellent condition, on the other hand, should bring between $25 and $200 depending on size, species, and condition. We have seen burls up to 12 feet in diameter; many of them measure around 4-5 feet across. Those may be worth anywhere from $600 to $1,400

Why is a burl valuable?

A burl is a growth on a tree that is often caused by some sort of stress or irregularity in the environment. The grain in a burl is usually very irregular, and the wood is often highly figured. Burls are also difficult to work with because they are often unstable and can cause problems during the drying process.

What is inside a burl?

The center of a burl is typically composed of small, woody tissue called parenchyma. Parenchyma cells are living cells that are responsible for storing water and nutrients in plants. Burs develop as the tree’s buds around it expand and fold into their developing form.

inside burl

Can you cut a burl without killing the tree?

No, once a burl has formed on a tree, it is not possible to remove it without killing the tree. Burls are actually woody growths that form around wounds or stresses in the tree’s bark. As the tree grows, the wood inside the burl continues to grow with it.

Do burls hurt trees?

Burls do not typically hurt trees, but they can be a sign of stress or damage. If a burl forms around a wound in the bark, it can help protect the tree species from further damage. However, if a burl is large and heavy, it can put stress on the tree and cause it to lean or even topple over.

Do burls grow underground?

Lignotubers are underground burls that develop around the base of a tree and beneath the soil surface. They’re not to be confused with above-ground burls on trunks or in a tree’s crown, although they develop in much the same way. Lignotubers, on the other hand, tend to be larger than aboveground burls – the biggest lignotuber ever measured (from a California redwood) was 45 feet in diameter and weighed over 500 tons.

burl grows underground

How can you tell if wood is burl?

If you’re not sure if a piece of wood is a burl, there are a few things you can look for. First, check the grain pattern. Burls typically have an irregular, swirling grain pattern. Second, look for eyes – small, round growths that resemble eyes or knots. Finally, feel the surface of the wood – burls often have a bumpy or warty texture.

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Oliver Wright
Oliver Wright

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