I could be wrong but I think that if you cut a ring around a tree (through the bark and into the wood) all the way around it, it will kill the tree.
If it was a large tree you would need a lot of anger and a chainsaw would help. It might get you busted if the tree was not yours.
I assume this is what “ringing” a tree is.
I wonder if this would work better if you alternated copper and galvanized (zinc) nails.
Yes, that’s right.
There was a tree in the parking lot behind our house, when I was growing up, that shaded our garden. My Mom asked the city to have it trimmed, but they wouldn’t. She was given the run around again and again. One particular Doper then is alleged to have ringed the tree, which was mostly likely to have been done on an early Sunday morning when no one would be about. This alleged event caused the tree to die, and the City did remove it, with no questions asked.
Of course, if that were the worst thing the particular Doper did in his life, then he would likely be justified in denying everything, instead of coming across as silly.
Sodium Chlorate should do the trick
When we bought a house we found a couple of barrels of in the garage and used it to kill weeds on the gravel drive. The stuff in the barrels was moist - I think I understand why.
A pine tree in the middle took ill and died.
Based on my experiences spilling gasoline on the farm when I was a kid, I’d say that was something easily available that would do the trick.
I was just about to say that.
This is an urban legend. http://www.gardenworld.co.uk/project-copper.asp See the note at the bottom.
Some years back, I was sold Pramitol for killing poison ivy. As it turned out, it killed everything but the poison ivy. I was warned, in person and on the label, not to use it for killing weeds in a crushed stone driveway if there were any trees next to the drive. They said it would kill the tree.
It’s especially more vicious when mixed with sugar? 
A disregard for floral norms, and indifference to the rights and feelings of said tree.
What herbicide would remain in the soil season after season, rain after rain?
You’re right. Nutrients flow up the trunk to the branches and leaves via the phloem, which is a thin layer of cells just under the bark. Cut through that – all the way around – and it’s like cutting a human’s carotid artery; death is certain.
That sounds like a herbicidal maniac.
Of course, a real sociopath, with respect for tradition, would use a chainsaw. 
You can kill a (deciduous) tree more easily than this. I killed several 24"+ diameter maples with a machete while cutting back poison ivy. The machete did cut into the bark fairly deep, but didn’t leave a much of a trace. 6 months later, 3 dead maples, and 1 very sick maple.
I certainly didn’t intend to kill the trees, and didn’t ‘ring’ the trees as such. I just hacked off the ivy around the trunk.
My point is that you don’t need to use a chainsaw or even do visible damage to a tree, they are far more fragile than I thought.
I’m not sure this would work with an evergreen, I’ve seen firs and pines that were pretty hacked up and still healthy.
Well, at least he’s only after trees. It’d be much worse if he was killing the corn and wheat and barley crops.
'Cause then he’d be a cereal killer.
It is much easier to kill a maple in this fashion than other types of trees (as you have noticed). I’ll leave the issue of whether poplar, ash and maples have “bark” to any botanists that might be about, but suffice it to say these trees do not have a thick layer of “dead skin” to serve as protection when you’re hacking at vines with a machete.
There are any number of commercially available herbicides that will kill a tree. Velpar will do it if poured onto the ground, there are others that are injected into the tree by cutting a slit with a hatchet and spraying the liquid into the cut. (Called the “hack and squirt” method)
I do think his threat that “nothing will ever grow there again” was hyperbole.
It would not be practical to try to kill a large tree with salt. Why apply 100 or more lbs of salt when a professional landscaper would have a variety of herbicides available to him?
And nails in the ground, copper or otherwise? Er, no.
Oddly, a few months ago some tree surgeons were working on a tree, I asked them what they would use to kill it and they said ‘it’s mainly salt’.
I think he’s mistaken for a different reason. Had to dump out over a keg of beer? I mean the words, they’re all English, but they just don’t add up. Couldn’t you have drank it later, or like, donated it to charity? (e.g. me)