Those wild berry bushes are raspberries/blackberries. This time of year you can buy those at some of the bigger home centers like Home Depot and Lowes. They will spread just like the wild ones.

Some roses are pretty but very thorny too. For example, The Fairy is a very thorny one. I also have barberry which is pretty pointy and for shade, mahonia, with pointy sharp leaves.

Rosa rugosa is very thorny, and doesn't need pruning, unless you just want to contain it. Rugosas are relatively fast growing, also. After a full season they should be a sufficient barrier.

There are several things to consider. How tall do you want the barriers to be? Do you have the right amount of sun or shade in the areas to help your selections thrive. What about water? And then, you want to know about the behavior of your barrier. Bramble berries never stay in the place where you put them. They run underground and can get to be problematic for the people you are NOT trying to exclude. If you decide on roses, do your homework. Some can be as invasive as bramble berries.

You also need to consider that no plant is maintenance free, and thorny plants are no fun to maintain. Whoever is doing clipping is going to get stuck. All prunings must be cleaned up, or anyone walking through the area without foot protection is also going to get stuck. Perhaps you just need a good strong thick hedge that would be more trouble than it's worth to push through?

All that being said, here are a few suggestions that come to mind:

Barberries: very thorny, very attractive. About 4 feet high and wide. Full sun. Drought tolerant. Deciduous.

Dwarf Yaupon holly: about 4 feet high and wide. Not thorny, but the branches are "pokey". I wouldn't want to push through a thick hedge of it. They do well in full sun, are drought tolerant, and disease and pest free. Most will do fine on just one shearing a year. Honestly, their natural form is so nice, that you may not find shearing to be necessary. Plant them fairly close together for quick fill-in (about a foot less than recommended).

Elaeagnus: large, thorny, evergreen, drought tolerant, full sun to part shade. They need alot of clipping until they fill in, but they grow fast. Some farmers use them for cattle fences. Need I say more? These are not my favorite shrub, but they would do the job. Look for the variegated varieties for more attractive looks.

Cleyera: evergreen, fast growing, beautiful foliage summer and winter, full sun to part shade. Virtually disease and pest free. Will grow faster with regular water, but are very drought tolerant. NOT thorny, but a good thick hedge of them would likely stop the vast majority of the traffic. The branches are pretty strong and sturdy. For a tall hedge, this would be my first choice.

There are numerous hollies that would do this job too: evergreen, berries, reasonably low care, full sun to part shade.

I'm sure you will get other suggestions too.

There is no limitation as to how far the plants can sprawl and we really don't care about the look of the plant. Evergreen or deciduous is OK as long as people will not want to cross the barrier. No-one we care about is likely to go near the area. The plants will get water for the first year and then they are on their own. At least 6 hours of sun at all the sites. We'd like the plants to get as tall as possible but 4' is about the minimum. The soil is your basic, red Georgia clay.

Hope this helps.

Rolf

Please don't consider Elaeagnus - it has become an invasive plant (non-native) in Georgia.

I think the brambles are a good idea and you'll have fruit should you ever want it (and the birds will thank you). I've tried to cross an open field with thick brambles (Rubus, that is) and it is very near impossible!!

Check in your local hardware stores now for what they have (don't buy the thornless ones, of course). You can also transplant wild ones - cut off the dead cane and just dig up the rooted parts.

I'm surprised nobody recommended mock orange. Someone on the Carolina Gardening forum was giving a mature one away.Tricky part is how to avoid the thorns while digging up the plant and lifting it for transport. You almost need a chain-mail blanket!

I meant 'poncirus trifoliata'

How about Erythrina crista-galli or crybaby tree. For me it grows more like a bush. The limbs are killed by hard freeze but can stay on the stump as a deterrent until the new shoots start to emerge.

Why has no one reccomended Cacti?

Prickly pears grow well for me (I know of some wooded trails where there are random clumps of prickly pear, growing wildly without any care)

There are lots of cacti that grow well in Alabama... Plus I bet it would be more attractive than the tangled masses of berries...

You could come to my yard and dig up all my brambles :)

I don't know if they transplant, but as someone said, they are basically wild berry bushes and they are very thorny and will spread.

Lots of luck with trying to keep trespassers off your property. Where I used to live, teenagers thought of my back yard as a cut-through to get to another neighborhood. Nothing, and I mean nothing would deter them. I don't know how tall prickly pears grow, but if they stay low enough to step or jump over, they won't be any help at all. Another alternative in addition to the thorny bushes is some prickly-leaved hollies, planted very close together. Some of them can be a great deterrent.

Agaves, planted close together, and they make many babies after 2 or 3 years.

Poncirus (Trifoliate orange), yucca (Spanish dagger), mahonia (grape holly), New Dawn rose.

Agaves are wicked,evil things and one thing that property owner has to consider is liability insurance. By planting certain items like agave that would cause serious injury to trespassers it could cause him far more $$$ in future lawsuits. Far cheaper to install a tall fence.

Mermaid rose is a house-eater, easily reaching 20 x 20, & its thorns are truly wicked.

Maybe Russian Olive, I know the grow in New Mexico and Colorado but not sure about Georgia. They have thorns that get to be over 2" long.

You might check into the rose Seafoam, too;
although it's sold as a ground cover, mine grew to over 6' tall, & it has millions of nice sharp little thorns.

It's been evergreen for me here in Texas;
although our winter temps seldom dip into the low twenties, this past year they went into the mid-teens a couple of times, & for 2 days we had 2' of snow on the ground (first time in my native-Texan life!), & still this rose remained green.

If esh-ga is reading this, I know it is guaranteed to push her invasive plant buttons; but after living and working in the State of Georgia for more than fifteen years, out of patriotism, I am compelled to recommend the Empire State of the South's state flower--the Cherokee rose (_Rosa laevigata_). Imported from China in the early 1800's, the Cherokee Rose is a beautiful, rampantly vining, evergreen rose, with horrid thorns and beautiful, single white flowers having gorgeous golden centers. It blooms lavishy in "high spring" with the azaleas and wisteria. When I lived in Valdosta, one of the most beautiful springtime sights in the Azalea City was a mature slash pine on Bemiss Road up which wisteria and Cherokee Rose climbed for many feet, flowering together with reckless abandon--a thing of beauty and a joy forever.
During the Antebellum Era, Cherokee Rose was used as living fencing around Southern pastures and fields. It creates a virtually impenetrable hedge--thick enough to keep out all but the most determined of Flannery O'Connors fabled "scrub bulls." No doubt, the Cherokee Rose can conquer those wretched little street urchins, or "no-neck monsters," or whatever.

Pyracantha has some nasty thorns, plus it's a nice plant with red berries in winter and it gets white flowers.