Inosculation – the natural joining of two trees

Inosculation – the natural joining of two trees

Inosculation is a natural, involuntary biological process (unlike grafting – a human induced process) where two trees (or sometimes roots or branches) grow together and fuse, creating a single, merged entity. This fusion occurs when the protective outer bark wears away, exposing the living layers, which then produce calluses that eventually form vascular connections, allowing them to exchange nutrients.

How this actually occurs

First, we need to know a little about how trees respond to wounds. When the outer bark of a tree is removed/scraped off, the inner tissues become exposed – specifically the cambium (tissue responsible for growth), the xylem (tissue responsible for transporting water and nutrients from roots to upper parts of tree), and the phloem (tissue responsible for transporting food and organic matter throughout the tree). A wound can occur when a branch breaks due to various reasons, or when two trunks abrade against each other as they sway in the wind.

Trees respond to wounds by producing scar tissue, (just like a human being) that grows relatively quickly to protect the exposed inner tissues. Eventually, the callus growth develops into ‘woundwood’, which resembles normal wood with organized cells that form the various tissues (xylem, phloem, cambium).

This phenomenon occurs when the friction between two trees causes the outer bark of each tree to scrape off at the point of contact. The trees respond by producing callus tissue that grows outward, thereby increasing the pressure between the two trees. This pressure, along with the adhesive nature of sap or pitch that exudes from the wounds, reduces the amount of movement at the point of contact. The cambia layers from the two trees come in contact and the vascular tissues become connected, allowing for the exchange of nutrients and water.

The video below shows a simplified version of inosculation

The next videos show more complex forms

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