We thought of the roses but decided we need something more "painful". I'll check on the hardiness of the Poncirus.

Barberry

Check out climbing 'New Dawn' rose. I can attest that it is painful. Many large wicked thorns and a vigorous grower. Rugosa roses also have good thorns and create slowly spreading thickets. Or consider adding some poison ivy to the fence.

My Dad had New Dawn along the fence beside his narrow driveway. You could not get out of the car without drawing blood.

One challenge will be protecting the prickly plants from the tromping students while they establish. So some sort of robust fence will be needed or the plants will never get a chance to make a barrier.

Ada, I am going to suggest some other actions.....as I am fully aware of this exact kind of situation.

First, what kind of damage are they doing? What does the fence have to do with it?

· Use the security camera to obtain pictures of students in the act. Take those pictures to any department that seems appropriate. I would start at the President's office and let it move downstream. The Dean of Students may also be a resource.

· Take pictures of the damage. If they are causing damage that results in repairs or replacements, document the costs.

You need to remember that a university isn't responsible for what their students do on private property, UNLESS you can prove criminal intent or outright vandalism. If that is the case, and you have the films and pictures, you should take the problem to your local police department.

If I know exactly what kinds of things that they are doing, I may be able to come up with a better solution than thorny shrubs.....which will rarely solve the problem. Please know that if you plant something that can cause injury to a trespasser, they have legal recourse against YOU. /:-(

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Yes: a new planting is not gong to be more effective than the existing fence and other features.

rhizo, Iḿ glad you wrote what you did. I cant put my finger on exactly why, but the idea bothers me. The homeowners have a right to have their property remain undamaged, they have a right to privacy and my sympathies are with OP. Somehow, risking eyes and skin to large thorns doesn´t sit right.

Well, I ripped out most of the barberry hedge the previous home owners had planted to discourage deer. It is prickly enough to discourage intruders but not lethal. (I left one red, Japanese Dwarf Barberry.) I think it is hardy for you. I doubt the Hardy Orange (Poncirus) is hardy for you..., talk about a 'nuclear option' though..., that plant is just lethal! Oh, the first place I ever did see one was on a college campus.

In a milder zone, I use hardy Opuntia, Yucca gloriosa and a hardy Agave around first floor windows.

plant some innocent looking shrubs such as gardenia or rhodedendron and put some poison oak to grow on the fence that should help although you could go with roses and poison oak