The beautiful, chaotic growth born from a tree's struggle to survive

Gardening · Published 18 October 2026 Swipe more like this →

In short: Highly prized by artists and furniture makers, burls are much more than mere knots. These swirling, dense growths are actually the result of biological stress, appearing as beautiful deformities caused by injury, fungi, or even bacteria. Beneath the surface, they hide a complex, interlocking grain that is as difficult to work as it is stunning.

A burl, known as a burr in British English, is a specialized growth where the tree's grain has developed in a deformed manner. Scientifically, this phenomenon is the result of hyperplasia—an abnormal proliferation of xylem production by the vascular cambium. This process is typically triggered by external stressors, such as physical injuries or infections from viruses, fungi, or the bacterium Agrobacterium tumefaciens.

While many burls appear as rounded outgrowths on trunks or branches, many others develop entirely underground. Attached to the roots, these subterranean burls often resemble bulbous protrusions connected by rope-like root systems. Because they are hidden, these growths are frequently only discovered after a tree has died or fallen over. In some species, like the coast redwood (Sequoia sempervirens), burls can reach staggering sizes of up to 26 feet (8 meters), potentially englobing the entire trunk.

The resulting wood is exceptionally dense and features a 'wild grain' of twisted, interlocked fibers. This makes the material notoriously difficult to use with hand tools or on a lathe, as it tends to chip and shatter unpredictably. However, this same resistance to splitting makes it ideal for heavy-duty items like mallets and wooden pegs. This beauty comes at a cost: the high market value of burl wood has led to the poaching of ancient redwoods in US national parks, where thieves use chainsaws to sever burls, leaving the parent trees vulnerable to further disease.

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