Great point about cables. I was speaking with a municipal arborist recently about the issue of cities and municipalities not using cables because of the possibility of taking on liability. Sometimes a cable in a multistemmed mess of a tree might be sketchy, but cabling a two stem, symmetrical linden fixes the issue, no doubt, and for a very long time. If the linden fails couldn't we blame a town for not cabling? If a cable fails and damage is done, can't the town say they tried their best? We have all seen cables fail but not when installed properly. And when failure occurs when installed properly, the blame can be put on the tree or Mother Nature?
The point is that I think we have come to a point where urban trees deserve and require a health record, a tag of some sort. Im sure this is happening somewhere and I don't mean reports or inventories, I mean cables installed with records and plans for revisits.
out of a hundred cabled urban trees, say 10 will fail without a cable. So if 90 cables are then installed for no reason does it matter? Better than removing 10 and risking the other 90. Remembering that you didn't cable the ten that actually needed it, you only cabled six as four looked like they had good narrow crotches but didn't and four had good crotches that just looked really bad.
As for generally speaking, identify weak crotches as best you can and cable and or reduce. Reduction severity is based on how bad the crotch is. The other option is risk it. Maybe No target, and the tree is not important as there is many others right close by.
When a crotch has stems that are corkscrewed then cabling may not be in line with the direction of probable failure. In this case reduction or in extreme cases including extensive decay, retrenchment might be best to avoid failure long term. Remember the biggest thing with both reduction and retrenchment is that the job is never done. You need to assess the tree response and reapply reduction or even thinning, often frequently depending on species and response. Risk grows back. Of the trees I've reduced once, a few have failed. Of the trees I've reduced more than once, none to my knowledge have failed but I'm sure time will change that. The point is once we regain control of a tree by regular FULL CROWN reduction and thinning, then the tree becomes almost storm proof.
Some trees need only cuts up to 1" and some need cuts up to no size limit. I'd say reduction is up to 3" or so then upward of that (retrenchment) you better have a good reason to make a wound that big. I often look at the decay wound in question. If it has consumed 18" of the cambium of a 70" circumference (22" diameter stem roughly) then you might want to make a few cuts up to 14" or so. On the other hand if the crotch is free of decay, a detailed and thorough application of reduction up to 1.5" cuts should be plenty, especially if applied two or three times in the first ten years of the intervention. Think of it as growth intervention. You want to disturb the natural growth. To avoid failure the natural leverage properties and taper can be manipulated. Not because we are better than nature, but because we want to reduce the tree before Mother Nature does. Silver maples grow fast, up and out to compete. We need them to grow more like sugar maples. More upright, quick but not too quick. Fast at first but then slower as they pass rooflines. We can project the better growth patterns from one species onto another.
Reduction is the future (and present to some degree) of good arboriculture. Trees will live longer, stronger, and will fail big stems less by the wind of the storm, as they are cut sensitively yet thouroughly by the hand of the arborist.
Don't thin out, thin in.
You can stare at a crotch all day and wonder and wander but if you reduce it sensitively, no harm is done and the tree is capable of more than it was before.
I just noticed what I said. Be careful not to get slapped when you stare at a crotch all day.
