Everyone has ‘how-to’ advice on pruning. Some is good, some not that bad, but most is just wrong. In defence of the bad, I suspect the issue is the term ‘pruning’ – a catch-all meaning to trim or cut away dead branches or overgrowth. But there isn’t just one sort of pruning, and herein the problem may lie...
How a person prunes roses is completely different to how you prune trees, and how you prune a fruit tree for fruit is very different to how you prune a fruit tree for appearance. You’d never prune a camellia the same way you prune a grapevine, and just to confuse things, you might prune an orange tree to enable a dove to fly through it (the Asian mystic way) – but you would never do that in New Zealand.
It doesn’t actually get any better for those who have undertaken formal training, as there seems to be pruning terms for the sake of having pruning terms. Trees, for example, can be pruned by crown lifting, crown thinning*, crown cleaning and/or crown reduction. In reality, all pruning results in reducing the crown, so we could call everything a crown reduction, but sometimes the crown is at the bottom of the plant, as it is with roses. There is the added factor of the placement of pruning cuts (node or internodes – unless you are taking a cutting, you should never cut at an internode).
So, back to trees. How do you prune a tree so its first permanent branch is 3m (as often advised) above the ground if the tree is only 2m tall? What is pinching? And, of course, pruning principles go out the window when you hedge, which is probably why most hedging is done badly. There is definitely no one-size-fits-all solution, but below are some basic guidelines to steer you in the right direction.
Ideal methods of pruning
In the knowledge that one size does not fit all, here is some ‘big picture’ advice:
Always think in terms of where the new growth will be. Shape your plants with new growth, not pruning cuts, and if there isn’t growth where you want it, leave something to grow into the gap.
Focus on formative pruning when the plant is small – get the structure right at the start (remove inward growing and/or crossing branches), then future growth will become quick and easy.
Always prune back to live growth, be it a bud or a branch. Make the cut as close as practicable to the live growth (but not so close that you damage it).
All pruning wounds. Even a correct pruning cut makes a wound, so keep the size and number of your wounds to an absolute minimum – if you don’t know for sure where to make a final cut, then cut at 90°to the branch or stem(it’s not going to be the correct cut, but it will create the smallest wound).
Don’t make angled cuts so the water can run off. Wood is waterproof – we age wine in wooden barrels and wooden ships sail the oceans. Angled cuts make larger wounds and require more effort, whereas smaller, non-angled cuts are easier and better for the plant.
Don’t apply pruning paste, paint or grease to your pruning cuts – it will do more harm than good and it will do no good at all (maybe in an orchard situation it might still be acceptable, but I don’t even think they do it any more).
Good pruning will result in the plant looking smaller but otherwise fine. If it is obvious that the plant has been cut, if there are stubs and odd branches pointing this way and that, that’s not pruning, that’s poor work.
If you are using a handsaw, then the branch you are removing will be big enoughto tear the bark if it falls, so remove the branch in two pieces. The first should be 100mm-200mm past where your final cut will be, then come back to as close as practical to the live growth and make your final cut (the smallest wound you can). If you are using a chainsaw to remove a branch and you don’t know for sure where to make a final pruning cut then stop it, put the saw down and walk away – you’ll only damage the tree and you’ll probably hurt yourself in the process.
Trees don’t heal, they seal. Remember this, because the mistakes you make will be sealed into the tree for the rest of the life of the tree.
When it comes to trimming a hedge, start at the widest point and trim it back as far as you can (but to live growth), then blend the rest of the hedge in to meet that point. The bottom/base of the hedge should be slightly wider than the top (this is to prevent the top from shading the bottom so an even growing face is made).
Pruning shouldn’t be complicated Just remember to make your cuts as small as you can – do the least damage.
Don't forget saw safety!
Lastly, keep your hands away from the sharp bits – handsaw injuries account for more lost time than chainsaw injuries in the arboricultural world. Keep your hands away from the sharp bits, cut away from your body and always use a chainsaw with two hands.
For tree pruning and general tree care, check out the website Trees are Good treesaregood.org/treeowner/pruningyourtrees
* Never undertake crown thinning – it’s old school, it’s wrong – don’t do it and if you do, stop it!
Mark Roberts is a qualified arborist and tree risk assessor with 25 years’ experience. Mark is also former President of the International Society of Arboriculture, and a past President of the NZ Arboricultural Association. Mark now heads an arboricultural collective based in Dunedin: robertsconsulting.co.nz