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All About Mesquite or Devil Trees
LA, the thorns won't rot on their own. So you can't just cut them down and the thorns go away in time. I think that is why the guy burned the trees, as it was the only sure fire way of destroying the thorns. Now this is according to someone that I knew, who lived in the area. They had land with quite a few of these trees. So he decided since they wouldn't decay or break down, he would burn them down. Well he got the fire going alright, but it got away from him. He is real lucky that he didn't burn his house down while trying to get rid of the mesquite. He is also the one who told me about the thorns. The tree is a legume, but who would want to get up in there and harvest the pods? NOT ME.
I have one of the Japanese Barberry bushes you mentioned. It is still alive, and I never do anything with it. It looked great against a golden yellow bush that I had planted next to it. Sadly the other one died a long time ago. I love the color of the bush, but know not to mess with those thorns. It is nothing compared to my Mayhaw though. The firethorn/pyracantha has white flowers that turn into red berries later. I only have one of them, thank goodness. I didn't realize how bad the thorns were, until mine matured. Maybe you had an allergic reaction to the Barberry thorns. You can also get a bad infection from some thorns of various trees and shrubs. Also people have lost their eye to some of them.
I think that shrub I had was called a Spanish Dagger. (for GOOD REASON) It is much worse
than it looks. Plus it multiplies freely. That one was given to me. Second thought, maybe I should let it grow back, I won't say why. LOLLLLLLLLLL.
Below are the thorns of a Mayhaw. The pyracantha has similar thorns to it. If you prune either, you need the heaviest leather gloves you can get.