How Does Bark Grow?
Bark doesn't grow in the same way as, for example, human skin heals. Instead, new bark develops as a byproduct of the tree's overall growth process. The key lies within the cambium, a thin layer of actively dividing cells located beneath the existing bark.
The cambium layer is the tree's growth engine. It continuously produces new cells both inwards (forming wood) and outwards (forming bark). This outward growth is driven by hormones, specifically auxins, which travel down from the leaves via the phloem (the tissue responsible for transporting sugars). These auxins stimulate cell division and expansion in the cambium, leading to the formation of new bark layers. As the tree grows in diameter, the older bark layers on the outside become compressed and eventually die, forming the protective outer layer we recognize as bark. (C, US Forest Service)
Bark Growth and Types of Trees
Different tree species exhibit diverse bark characteristics. Some, like cork trees, have bark that readily regrows after harvesting. (Reddit) Others, such as Manzanita trees, have peeling bark due to stem growth outpacing bark expansion. (Lansing Garden Design) This highlights that although the underlying process is similar, the resulting appearance of bark varies widely depending on species-specific characteristics and growth patterns.
Understanding the Growth Process
Here's a simplified breakdown of the bark growth process:
- Hormonal Signals: Hormones (auxins) from the leaves stimulate the cambium.
- Cambium Cell Division: The cambium produces new cells outwards.
- New Bark Formation: These new cells differentiate into bark tissue.
- Expansion and Shedding: As the tree grows, older bark layers are pushed outward, eventually becoming compressed and dead.
In essence, bark is the outward manifestation of a tree's ongoing growth and development process, driven by the cambium's continuous production of new cells in response to hormonal signals. The appearance of the bark, its texture, and its rate of shedding varies considerably across different species. (YouTube, Quora) It is important to note that while some trees have a remarkable ability to regenerate their bark, damaged bark does not regenerate in the same way as human skin. (Brockley Tree)
