Hedge trees were planted before the invention of barbed wire. The idea was they were tall enough that a horse couldn't jump over; strong enough a bull couldn't push through; and thick enough that a boar couldn't squeeze through. Then, to make things interesting, there were thorns that grow to about 6 inches long. Fence posts made from hedge are so hard they don't rot, and are impervious to termites and other insects.
End of lesson
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So, since we've had something peculiar to my part of the world....how about something found only where you are?