I use some nasty sticky plants here in Hawaii to deter trespassers. A double or triple row of ornamental pineapple is nasty. Mix in some Hawaiian poppys and it can be quite a prickly barrier. I use this combination down at my seed farm and nobody has tried to walk through it yet. Across the front of the seed farm along the fence I have blue agave. People don't want to tangle with them either. Quite nasty. Then there is bougainvillea. It takes a few years, but it can make in impenetrable barrier. People use it here all the time. My horse won't try to bust through it, it's so thorny.
It's never too late to start! I retired to homestead on the slopes of Mauna Loa, an active volcano. I relate snippets of my endeavor on my blog : www.kaufarmer.blogspot.com
posted 5 years ago
The Honey Locust Tree/Bougainvillea are the winners for me!
Thank you so much for the help!
I ordered the honey locust tree seeds and have access locally to the bougainvillea
Location: Missoula, MT US Hardy:5a Annual Precipitation: 15" Wind:4.2mph Temperature:18-87F
Since you have chosen the Honey Locust, I think it would be advisable to read up on these three threads located here, here, and here about the Honey Locust. Also, depending on your seed source, you may have been given the thornless variety; did you check to make sure it was the thorny kind?
This is a short video describing honey locusts and black locusts:
According to Wikipedia, Honey Locust shares similar rot resistant properties as black locust. In addition, it comes with its own natural nails and tire-poppers, too.