Trail Notes: Inosculation
There is a tree grouping on a trail at Fox State Forest that I stop at every time I pass it. Multiple birch and hemlock trunks wound together, at least four points where the trees have fused into a single structure.
What I'm looking at is inosculation, the process by which branches or trunks in sustained contact slowly grow together. Friction and pressure wear away the outer bark at the point of contact. The trees respond by producing callus tissue that grows outward, increasing pressure between them. The sap that exudes from the wounds acts as an adhesive, reducing movement at the contact point. Eventually the callus develops into organized cells forming the full range of vascular tissues: xylem, phloem, cambium (Burnham & Wason, 2022). Once the cambium layers of two trees make contact and fuse, water and nutrients can move between them through the shared vascular connection, though whether genetic material transfers across the union remains an open question in the research (Burnham & Wason, 2022; Melnyk & Meyerowitz, 2015).
Birch and hemlock trunks intertwined. You might also notice the peculiar formation at the trunk base where you can see long roots leading up to the main trunk. These trees grew up on/around a nurse stump that has since decomposed.
Inosculation most commonly occurs between trees of the same species, but I've seen more incidents of this with different species. These cross-species fusions sometimes produce what researchers call "false grafts" where the trees appear joined but have not formed a true union of conductive tissue (Burnham & Wason, 2022). It is unclear whether this might be the case for those birch and hemlock in Fox State Forest, but hemlock, white pine, maples, birches, ashes, and American beech are among the species most prone to the phenomenon (Burnham & Wason, 2022).
A few days ago I was scouting a trail for an upcoming nature journaling workshop and found an example within a single tree. A two-trunked beech, its trunks connected by a branch with no clear origin. This is actually the first time I've seen the phenomenon in a single tree.
This beech tree at the Knights Hill Nature Park in New London, NH, has a spectacular example of inosculation. I wonder from which side the branch first grew?!
How this connects to my work
These are the observations that stop me on the trail. Not the dramatic or the obvious, but the places where something slow and patient has been happening for decades without anyone noticing. This is what I'm looking for when I'm out with my journal, and it's what comes back into the studio with me. Work that is not only beautiful to the eye, but carries hints of these forest stories.
References
Burnham, R., & Wason, J. (2022, February). Inosculation: Making connections in the woods. University of New Hampshire Cooperative Extension. https://extension.unh.edu/blog/2022/02/inosculation-making-connections-woods
Melnyk, C. W., & Meyerowitz, E. M. (2015). Plant grafting. Current Biology, 25(5), R183–R188. https://doi.org/10.1016/j.cub.2015.01.029