For the past few months I have been writing pruning specifications, or more correctly I have been removing pruning specifications. I’d love to say it’s a less-is-more situation, but I’ve actually been writing more to inform the reader of less – why less is good.
Arboricultural pruning specifications; cleaning, thinning, lifting, seem to date back to the time of pruning-paste; back when we did things because what is what we did. Science came along and put a stop to pruning-paste, and that was good. Science was the excuse everybody was looking for, but in reality, it was a mucky job that nobody liked doing. But cleaning, thinning, lifting were different, they were easy jobs with obvious results, jobs that could be explained away without science; ‘yes, yes the wind can now pass through’, ‘no, no we always remove the dead, dying, diseased, crossing, and internal branches’, or ‘yes, yes just a little bit higher and it will look like a tree again’. It is not like the literature (the science) wasn’t there to say that sort of work wasn’t helping the tree, but these jobs were low-hanging-fruit; value for effort for income, these were the jobs to do – and rightly or wrongly arborists did them.
An arborist by definition is a person who cares for trees in order to preserve them – one could argue that the only thing being preserved by cleaning, thinning and lifting trees, is the supply of work but that would be a little misleading. Pruning specifications on cleaning, thinning and lifting still exist, so one can’t put all the blame on the arborist – there is an expectation on the arborist to do the work, and for that those that want the work done there is misguided belief that these practices are actually good for the tree. This is a case of supply and demand – but those that demand, are demanding the wrong things.
By removing the dead, dying, diseased, crossing, and internal branches (crown cleaning) the arborist will most likely expose the internal branch structure to more light, and this can stimulate dormant buds (in trees that have them). Those buds will grow into shoots and within a few years there will be dead, dying, diseased, crossing, and internal branches. So, the tree owner needs to get an arborist in, and around and around we go. The net result is that the client gets to spend money, the arborist gets work and the trees get a cycle of wounding with limited periods of recovery. For trees that don’t have dominate buds, the work most likely changes the internal conditions inside the canopy to such an extent that it will generate more, dead, dying, diseased and internal branches. So, the tree owner needs to get an arborist in again, and around and around we go – but this time the tree doesn’t get a cycle of wounding with limited periods of recovery, the tree gets a cycle of wounding leading to an increase of branch failure (multiple pruning events force the foliage out towards the branch ends, the branches become tip heavy and start to fail).
And then there is thinning. By removing selected internal branches to let the wind through (thinning), you are actually removing the trees ability to dissipate the kinetic energy (movement by wind and other forces). The net result is increased wind loading on the branches that remain, and most likely an increase of branch failure – thinning to lessen the chances of branch failure, is more likely to lead to an increase of branch failure. And if the thinning is done to increase light… see above for stimulated dormant buds and a cycle of spending, work and tree harm.
Lifting is something else, but I’m not sure what. Lifting; removing the lower branches to keep the natural form and balance of a tree, has to be one of the silliest specifications ever written. What this specification is actually saying is; ‘make the tree look like a lollypop because that is what trees actually look like’.
The natural form and balance of a Lollypop tree
Maybe the original author of this specification was having a psychedelic experience, or maybe natural forests of lollypop trees exist, and I am yet to find them – who knows. But see above with foliage getting pushed [out] up towards the branch ends, becoming [tip] top heavy then failing – the cycle of spending, work and tree harm and/or stimulated dormant buds (on the trunk) and a cycle of spending, work and tree harm. We could also add in increased chances of root-plate failure, torsional loading and shear-plane cracks, but you get the picture.
So, what am I specifying in my less-is-more pruning specifications?
Obviously, the statutory stuff remains, clearances over roads and footpaths, clearances from power lines and traffic signs are what they are and a simple reality of urban trees.
Having big bits of deadwood fall on people is also problematic (even though the chances of it ever happening are extremely unlikely). Most deadwood is actually beneficial, so I only recommend removal of the larger bits above places where harm and/or the associated outrage could occur – associated outrage, being the ‘it could have killed my child, if I had one, and if it was there at the time… but I don’t and it wasn’t, but it could have if it was, so you need to cut all of your trees down – because trees kill babies’.
I don’t recommend generic cleaning, thinning, because apart from mostly harming the tree, they don’t tend to achieve the result the tree owner wants – maybe in the short term, but almost never in the long term.
Good arboricultural practice (what I am recommending) is mostly, leave it alone (do nothing) or use branch end reduction to get the results you are after. Branch end reduction is exactly as it sounds – reducing the length of the branches by removing the ends. The internal branches are retained, and the arborist works from the outside, back in – by keeping the internal branches there is something to dissipate the kinetic energy, and the chances of stimulating dormant buds are reduced.
I do recommend formative pruning, for those that have a form, purpose or plan in mind, otherwise, formative pruning for formative pruning sake is just tree cutting.
The biggest problem I find in recommending branch end reduction, is that most trees of any age have been cleaned and thinned, several times over – so finding branches to reduce back to can be quite difficult. The other problem – which really isn’t a bad thing, is that the skill level required to undertake branch end reduction work is greater than the skill required to clean and thin (gut) or lift; so, specifying reduction work limits the work to skilled arborists – so not a bad thing.
So, I have been writing pruning specifications so those that demand work, and those that do the work can start caring for trees in order to preserve them.
I like that you didn’t even mention ‘topping’, which still seems to be the only term of reference for most kiwis when they think of how to ‘manage’ a tree.
Trying to convince clients that branch tip reduction is the only plausible option for management and that it should only be adopted if it absolutely needs to be is starting to feel a bit like introducing astrophysics to a convention of flat earthers (which unfortunately implies a level of superiority, which is unintended and unfair – because people can only know what they’ve so far been exposed to).
Here’s to changing the game one tree at a time!
Standards for NZ?