It takes a lot to kill most trees. They’re so well adapted to being sedentary giants, cutting off one limb here or one limb there is pretty inconsequential to their ability to live. Yes, they deal with setbacks and stressors like any living thing does. Some trees, as you probably know, basically refuse to die. If you completely remove a willow or a mulberry tree, even just leaving the stump is enough to completely regenerate a crown to continue living. This adaptive capacity is one of many reasons trees are so damn amazing.
A mentor and good friend of mine used to adamantly say removing certain limbs would kill a tree. He lacked some articulation on his argument, but he is correct in an indirect way. The tree can handle extensive loss of the canopy and recover. Yes, it will deal with decay issues the remainder of its life, but most mature and veteran trees do. But what he means isn’t so obvious. It is possible to kill trees in the urban forest where we live, without actually killing them. Let me explain what my mentor was getting at.
Example tree
Jeremiah’s hand for size reference. Saint Clair Shores, MI
When arborists comply with everything a homeowner wants with their trees, we end up in a scenario like this:
This tree wasn’t a tree I personally assessed or worked on, I just happened to see it. Here on this silver maple, a massive arm has been removed from the tree. It’s difficult to determine when this pruning was done, but I’d reckon 12-15 years ago.
About a third of the entire canopy was missing as a result of that large cut. The remaining canopy was sparse, full in some spaces and decrepit in others. Advanced decay has been allowed into the trunk, and now some of the tree parts are potentially unsafe to the houses or cars parked near it.
This brings me to my main point, this tree is now likely to be condemned. This tree can come back and restabilize, but in tree-time. Failures in long term thinking, and failures in understanding that trees operate on a time scale that lasts much longer and moves slower than our own, have left this tree in a state where it can be condemned.
Now, all things being fair, it is possible this example limb suffered catastrophic failure during a storm and had to be reduced to this point at the trunk. There are alternatives to completely removing a damaged limb, and avoiding allowing advanced decay into the trunk. In modern times, parts of the crown that get blown out by wind can be regrown by the hands of time and arborists together. Based on the type of tree work that goes on in this city where this picture was taken, leads me to believe that this arm was removed by choice, and not as a last resort. But the truth is I am not certain in this case.
Tree-Time
The point is still there to be made. Removing large organs off anything is detrimental, especially trees. Yes any pruning is damaging, but sometimes it is necessary in order for us to coexist with trees. Modern arboriculture is as minimal as possible. Gigantic cuts like the one mentioned above won’t kill a tree outright, but it results in us condemning trees because they become either unsafe or undesirable. Not because they’re necessarily dead.
This large cut on this maple takes a very long time to close over. Trees will close their wounds, not heal them, in order to exclude oxygen to their interior. While oxygen is available to the inside of the tree, decaying fungi and microbes can continue to decay the tree. The faster the tree can close a wound, the less extensive the decay is. This is a reason why it is wise to avoid cutting any major limbs, and proper cuts are located on the peripheral parts of the canopy where the cuts are the smallest, and can thus close faster.
Altering the crown shape by that huge measure has another negative impact on the tree. The tree grows to accommodate the stresses it endures; its own weight, and the dynamic forces of the wind (and also to optimize photosynthesis). Large modification to a tree’s crown results in the retained canopy being exposed to winds that it has never been exposed to. This can be bad because wood can’t adjust very quickly, and now even moderate winds can cause branch failures. This isn’t to say that it will happen, but removing large parts of the crown increases the likeliness that branch failures can happen.
My mentor wasn’t saying “removing these huge limbs will kill the tree”. What he was saying is removing huge limbs will eventually lead to a reason to remove the tree. Tree’s aren’t so linear in their life cycles. Just because it looks rough now, doesn’t mean it can’t improve or restabilize. Trees operate at a slower pace, and we sometimes don’t award them that privilege.
Saying No
Our choices as tree owners and arborists have long lasting impacts on trees. The trees we remove aren’t always justified in being removed, a tree looking undesirable doesn’t necessarily justify removal in responsible stewardship. Talking to a dutiful arborist can help sift through perceived risks and actual risks. Arboriculture has come a long way in the last 15 years scientifically, but the industry is nearly at the same stage 15 years ago, and finding good arborists is a challenge.
The sign of a mindful arborist is one who says no.
How to avoid accidentally condemning a tree
Education is the biggest obstacle preventing people from making wise decisions with their trees. If arborists are to say no and refuse to do overdose pruning, it could make the tree owner take a step back and scratch their head. Walking away from easy money makes people wonder, and hopefully look beyond their less-informed position.
For arborists, we need to hold true to our ethos. We’re entrusted to make the best decisions for the tree’s long term health, so we’re to stand our ground against malpractice. Yes, taking this huge branch off will not kill this tree. But its desirability decreases long term, and that can lead the tree to be removed. The homeowner will never know, in twenty years, the cuts you made today will compromise the entire tree. But you’ll know.
For homeowners and tree owners, please listen to your arborist if they say no, and ask for their recommendations. But still don’t take everything you hear to heart. A less informed arborist or a predatory arborist may not think there’s anything wrong with removing large entire arms of a tree. The safety concerns one may have for a particular limb can almost always be mitigated without entire removal of large limbs. Ask for their qualifications, an ISA Certified Arborist is a decent measure of a qualified arborist. Or better yet, ask them why they’re an arborist.
It is deeply unsettling and disappointing that bad tree work is the norm.