As a tree slowly grows, it is constantly changing itself to better withstand local stressors.
Roots change direction and shape depending on the growing location, chemical leaf defenses are constantly fine-tuned, and branches stretch towards the closest available light. The insides of trees are also modified over time in order to help them survive.
An easily observed example of this is in the wood grain of a tree, which is a unique arrangement of wood fibers in the xylem of the tree. This is the woody section beneath the bark that helps move water and nutrients throughout the plant.
Even though most trees have distinct wood grains and tend to create wood fibers in typical patterns based on their growth habits, they can also alter this structure in times of need.
Spiral grains, for example, help certain trees distribute water evenly while also giving branches more resilience in strong winds or snow.
Trees can also strengthen areas of high stress or damage by creating different specialized patterns of fibers.
Many of the changes that a tree undergoes throughout its life can be seen in its wood grain, and every board or bowl tells a brief life story of the tree that made it.
Grain changes are normally very subtle and slow to develop, and rarely deviate too far from the other trees in a species.
In some cases, however, the xylem of a tree can be rapidly and chaotically changed seemingly without the tree being in charge at all.
Trees can develop large woody growths in areas attacked by bacteria, virus, fungi, insects or a combination of the above.
Called burls, they usually bulge out from the tree as a spherical mass, and can occur in the roots, trunk and sometimes even branches.
Despite their abnormal appearance, burls don’t do much actual damage to the tree and seem to do their part in nutrient and water transfer.
Some scientists believe they are formed by an intruder in order to create a hospitable place for them to live. Interestingly, after extensive research over many years, no-one has been able to nail down what exactly causes each burl. It may be that some trees possess a genetic disposition towards burl creation in the face of certain pests as well. Whatever their root cause, burls grow as the trees age, and instead of normal wood grain the grain in burls is twisted and incredibly dense.
This can make burls difficult to carve, however it also creates beautiful and unique patterns that are popular in everything from bowls to fancy car interiors. The beauty in burls is only matched by their rarity, since they only develop in very few trees (sometimes seemingly at random) and can take over 30 years to fully mature.
This led to extensive programs, especially in the 1930s and ‘40s, geared towards figuring out how to trigger burl growth in trees. They were never truly successful.
While large burls are especially eye-catching, there are a wide variety of wasps that use similar yet smaller structures in order to raise their young. Some wasps lay their eggs inside of the twigs, branches and leaves of plants.
Using methods that are largely unknown, the wasp then triggers the plant to grow special structures called galls normally about a quarter or smaller in size.
Each species makes a unique gall depending on the cocktail of chemicals, viruses, fungi or other mutation methods they use. Their young then spend the next year or two feeding off of the gall before emerging and beginning the cycle again.
These galls are often then used as housing by a wide variety of other animals, and become a sort of plant hostel for wandering wildlife.
Brannen Basham and his wife, Jill Jacobs, operate Spriggly’s Beescaping, a business dedicated to the preservation of pollinators. Contact him at firstname.lastname@example.org.