Trees "calculate" which branches to drop based on data they gather as they grow. A competent and experienced arborist knows how to read the tree and simply safely cut off the branches that the tree was already intending to drop so that it doesn't fall on your house or whatever. Inexperienced arborists often ignore this key dendrology fact and may totally butcher your tree. In the process they can create an even larger risk of a tree falling over onto your house during a storm
It's called cladoptosis (basically self-pruning) https://en.wikipedia.org/wiki/Cladoptosis
EDIT: since I'm on the topic of bad tree trimming, NEVER TOP YOUR TREES https://www.arborday.org/tree-resources/dont-top-trees
I'm an arborist since 2022 in the UK and yes, never top trees. But...
There's three scenarios that come to mind in which it's somewhere between "acceptable" and "totally fine for some reason".
One, it's conifer hedge (the types popular in the UK) as these typically respond very well to being topped. It's what makes them a nice tidy hedge. I'm specifically referring to hedges above 3 meters in height. If you ever worked a hedge like this you'll quickly realise the topped stems are the platform to work off. These hedges can be maintained like this for years. For some reason, topped hedges are completely fine with being topped.
Two, it's either topping or removing. Arguably neither is ideal, but some retention is better than no retention. Topping puts the tree on senescence pathway and gives the ecology time to transition from alive to dead and dying. Whereas removal just makes the local fauna get confused about where the tree went.
Three, veteranisation in woodland settings. If there's a distinct lack of standing deadwood and age variation in a population of species in a given woodland NVC type, the topping and verteranising could be a positive management approach on a sample of trees.
This advice is very specific to the UK and especially on point three to the NVC woodland types. Generally though, prune properly at the correct locations, using proper technique being mindful of the structural loads and balancing of the tree. Topping generally, "because reasons" isn't an ideal approach at all.
The problem with number 2 is that it creates an allowance for people to plant the wrong tree in the wrong place and have fallback instead of being rewarded for their complete lack of forethought by having their tree summarily removed.
One of the cities on the east coast did a complete ban of planting anything but dwarf trees under utility lines. I don't know if you've ever seen an oak or a big leaf maple pruned to not tear down power lines but they look like something out of a Tim Burton movie.
Going forward, the answer should be removal, because otherwise the public will never learn, and you're enabling bad behavior, in the codependent sense of enabler.
> Topping puts the tree on senescence pathway and gives the ecology time to transition from alive to dead and dying.
Is this why the council recently topped a tree on my road that's been breaking up the pavement? We thought they were cutting it down since they dug up all the tarmac around it, but they just knocked the top off, taking something like 98% of the leaves with it, and then put fresh tarmac over the exposed roots. We've been puzzling over that for a week...
Hard to know with council works. Sometimes the work is great, sometimes it is a horror show. This sounds like more of a mis-managed tree that got too big, created too much liability in terms of legal risk and had to go. Rather than remove it from the landscape, leaving the stems does actually provide some green infrastructure benefit.
Isn't a more proper treatment (assuming the tree itself is healthy) to bump up the pavement target height like a foot or thereabouts and put down some slope smoothing ramps to limit how much it acts as a speed bump? I'd assume it would involve hydrovac digging down between the roots a foot or two deeper than the sub base the roots appeared to believe in, to guide future growth of those roots down (by making that direction easier than to break the asphalt again).
Or perhaps literally just grinding (or otherwise prepping/cleaning by however is suitable given the presence of these roots) the fractured asphalt to improve bonding, and following with a good layer of fresh asphalt over top thick enough to keep the roots deep/the pavement surface resilient against the next decade of the root's growth? Ofc. including start&end ramps to not make an excessive speed bump.
If it's thick enough future crack fixing should probably only require a prius-parking-spot-sized heat lamp/"grill" placed over the cracked asphalt until it's soft throughout the full depth of the cracks, and then run a compactor/stomper over it to smash the malleable asphalt smooth. If needed that's the perfect time to spread a wheelbarrow of fresh hot asphalt in the heated cracks to restore decent coverage thickness over top of the roots. Maybe first grind it down an inch or two to get rid of the weathered topmost bit, but otherwise asphalt is pretty much unlimited recycling suitable, or at least we haven't yet really run out of demand for fresh asphalt to get rid of the used asphalt we're digging up by cleaning it a bit before mixing with new ingredients to dial in target softening temperatures and gravel composition...
I suppose if a slow death is the goal then topping is a great strategy.
>NEVER TOP YOUR TREES
they do it where I live because the branches bang against apartments' windows when it's windy. I don't think there's another low-maintenance solution.
Coppicing or pollarding are both well-historied techniques that can be used to keep trees growing short. They differ significantly from topping and require a lot of expertise. They also have to be started when the tree is young
This is often not useful advice, as it is common to acquire responsibility for a tree than has been badly managed. The GP's link actually gives a solution for this case: pruning more accurately over a slightly longer period.
More generally, I've found as the maintainer of a building that while mainstream practices (of property generally, not specifically trees) often undershoot good practice, heritage techniques are often impractically expensive, and function more as a status signalling mechanism than really as a way of doing better. Even more generally, economy-wide; there is a tendency to criticise the mainstream but then promote expensive, semi-artisanal products and services, which while better, simply offer an escape valve to pressure for reform. Better techniques can only benefit the populace as a whole if they are cost reduced under the discipline of serving the mass market, not just offered as a premium version for the well-to-do.
Well I agree it'd be ideal for our society would be organized in such a way that effective semi-artisanal trades are cheaper than practices that do more harm than good.
The real advice I should've given was to construct protection for a window or hire a certified arborist to do a proper thinning of the canopy. But I wanted to remain on the topic of interest dendrology info
Fair enough- I did wander rather far from the topic
>NEVER TOP YOUR TREES
Kind of annoying when all the fruit is several meters out of reach
I wonder if this pertains to crop trees. A lot of crop trees are trained to stay smaller or grow in helpful shapes, such as with espalier training.
I was about to come in and say - orange groves are ALWAYS topped. I worked at the California Citrus State Historic Park, topping was done frequently. Same thing for most any orange grove from Cali to Florida. In fact, they're basically topped and hedged around explicitly to keep their size, shape, and productivity.
Fascinating! Where is this data stored? I love the idea of a Tree DB queried via TreeSQL.
It's basically a decentralized algorithm involving sugar defecits, auxin signalling, calcium flooding whenever cells stretch (due to gravity or wind), and ethylene release.
Trees can use all these signals to know which branches are being shaded or dealing with a lot of wind, which side it's being pulled towards more, etc.
Trees also optimize for their overall wind profile. Dropping branches that cause it more drag than they are worth in the sugar they make. The lower their wind profile, the lower the risk of the whole tree being uprooted during a storm.
When humans cut the wrong branches, it throws everything off balance.
Fascinating stuff. Reawakening my interest in arborist stuff ("arborism"?). Thank you for posting.
Reminds me how we have a local database from our city government with the exact location, what type of tree it is and more, updated relatively often: https://opendata-ajuntament.barcelona.cat/data/en/dataset/ar...
Different level of "Tree DB", I know, was still reminded that I at one point did something that required us to have a pipeline for downloading these trees location.
Apparently our city as 1/4 million trees and over 500 different species! https://ajuntament.barcelona.cat/espaisverds/en/management-a...
When you look closely, plants are made of many overlapping and highly sophisticated molecular state machines. The particular balance of select signaling molecules in a specific place within the plant triggers different response behaviors.
It's super fascinating to research all the different little mechanisms plants use to drive their growth and development. As an embedded developer, I find molecular biology strangely compelling. It's fun to see the "glue logic" nature evolved to solve all kinds of problems
Because they B-Trees?
I have a fun entry to the exception to the topping rule. I have a diseased sycamore that was really struggling. The disease was primarily at the top of the tree. We were going to cut it down to prevent neighboring trees from being infected or the tree from falling. The cutting company had a “hold my beer” style suggestion that topping it would bring the tree back. Boy did it. It’s flourishing with new branches from the cut and beautiful coverage. The fungus hasn’t come back and I’m not worried about it dying and falling on my house. Everyone wins!
I'd like to grow bonzai. I have zero prior knowledge. I suppose what you mention applies. Would you happen to have any good resource that applies to bonzai science please?
https://www.reddit.com/r/Bonsai/wiki/walkthrough/