When Caring Becomes Meddling- Part 1
Well hello there! It’s been awhile. I’ve been hibernating from the internet- it tends to be my habit during the cold winter months. For me, if the activity doesn’t involve bundling up and moving around in a snowy landscape, then it falls by the wayside until the world begins spinning towards spring again.
I love the winter landscape. It is during these (sometimes) snowy months that the world is stripped down to it’s bare bones and a raw beauty emerges- one that can’t be seen when the distractions of foliage and flowers fight for our attention. In the winter, form and structure prevail (accentuated by a blanket of freshly-fallen snow)… and it is glorious!
Winter is also an interesting time of year because landscape issues tend to really stand-out in the barren world: poor branching structure that arises from incorrect pruning is no longer masked by foliage, evidence of disease in landscape plants can often be revealed as sight-lines into tree and shrub canopies open up, and finally, questionable horticultural practices can stare us in the face.
On one wintry run I stumbled upon this…
Now orange emerging from a trunk is not exactly a normal thing to see, especially during the winter, so this definitely stood out like a sore thumb. Sure, some fungal diseases produce bright orange fruiting bodies during the growing season (i.e. various rust diseases or Chicken of the Woods/Sulphur fungus) but this was something different. This was an intentional placement of spray foam into a cavity within the tree… and it wasn’t just this one little spot, the tree was full of these patch jobs!
Let’s backtrack for a minute and take a look at wounds and cavities…
Cavities of various sizes and locations on the tree can be found everywhere!
Cavities are the result of decay (which in turn is caused predominantly by fungi and also bacteria). Improper pruning techniques as well as storm or construction damage are just a few examples of injury that can result in decay within a tree. In general, trees are able to ‘compartmentalize’ decay- separating diseased wood from healthy wood with a type of barrier within the tree. While the process of decay is one that a tree cannot halt, it is one that the tree can effectively slow through compartmentalization (with some tree species better at it than others). Trees will also react to decay by trying to outgrow it- adding more wood to the area near the problem (a way of reinforcing the weakened area).
Cavities in the making: the removal of large branches coupled with poor pruning cut locations means that the tree’s ability to heal itself has been compromised. Without being able to heal, the wound site/excess material begins to decay and this eventually leads to cavity formation (The photo on the right illustrates more advanced decay giving way to a cavity).
Gardeners, homeowners, and tree lovers tend to be meddlers. We look at cavities and decay and instantly feel the need to do something to help the tree. The thing is, the tree doesn’t necessarily need our help and it is quite possible that we can make things worse. If we do anything that compromises the barrier between diseased and healthy wood, we can speed the progression of decay within the tree (this is obviously bad!).
So what’s up with the expanding foam?
The rationale behind the use of expandable foam is that it can keep animals and moisture-holding debris out of the cavity. It also fills the space where water could otherwise collect. Moisture is necessary for the proliferation of decay organisms so the idea behind the expandable foam is to eliminate this scenario.
Being a flexible and non-abrasive material, it is also thought that expandable foam is kind to the interior of the cavity as the tree sways and grows around it- it will not rub and break through the ‘barrier’ between healthy and compromised wood- a concern with concrete or bricks- fillers that have been historically implemented to fill cavities. (Concrete, brick, mortar and stones have NO place inside the cavity of a tree! Incidentally, our case study tree had also been filled with concrete in some places. Poor thing.)
With all that said- if the expandable foam is not applied correctly, it can trap moisture within the cavity and hold it there. It can also prevent a tree from properly healing over. The type of foam used, how the foam is pared down to the cavity, as well as the coating used over the foam are all considerations for proper application of this technique. For these reasons, I would argue that the use of expandable foam in cavities is an arboricultural practice that should only be prescribed and implemented by a professional (ISA certified arborist) in very select cases. Even with that, I can not find any recent scientific research that suggests expandable foam is a valuable cavity repair technique. Finally, it is also important to keep in mind that when “decay is at play, get the professional’s say” (yes, I made that up just now)- decay can affect the structural integrity of the tree, so it is important that an arborist is brought-in to examine the extent of the decay and determine if any actions are required to mitigate the problem.
In the case of the ‘foam tree’ above, many of the cavities (and resultant patches) are small- there really was no need to meddle. There are also very large cavities and areas of significant decay on both the trunk and primary branches of this tree- these issues would certainly not be solved by expandable foam and require the attention of an ISA certified arborist. So in the end the liberal placement of foam patches has accomplished nothing for this tree except the creation of a blight on the winter landscape… and the inspiration for a blog post ;)
Stay tuned… while we are talking about meddling, no discussion would be complete without addressing wound dressings… coming up in a future post!
The sun is setting on winter… thoughts now turn to spring!
References:
American National Standard for Tree Care Operations- Tree, Shrub and Other Woody Plant Management- Standard Practices (Pruning). ANSI A300 (Part 1)-2008.
Gilman, Edward F. 2002. An Illustrated Guide to Pruning, 2nd Edition. Delmar, Cengage Learning.
Lilly, Sharon J. 2010. Arborists’ Certification Study Guide. International Society of Arboriculture.
Smiley, E. Thomas. Bartlett Tree Experts. (n.d.) Research Laboratory Technical Report: Cavity Filling. https://www.bartlett.com/resources/cavity-filling.pdf
University of Florida. (2020, January 21) Landscape Plants. Hollows and Cavities. https://hort.ifas.ufl.edu/woody/cavity.shtml