Native to the Central states, Honey Locust is hard to beat as a barrier plant. It transplants well, grows in most areas, is undemanding regarding soil—and has first-class thorns. This one grows in northern Ohio. Photo: © Greg Hume, via Wikipedia

Everybody has a favorite burglar alarm: bells, sirens, barking dogs. My favorite was the pitiable cries of a prowler who stumbled headlong into my strategically planted Teddy-Bear Cholla cactus. Barrier plants, as landscape architects and security pros call them, cover the spectrum from ones that warn a trespasser “Going here will be painful,” to ones that tell an intruder, “Thanks for the DNA samples, but don’t you think you should now run along home or to a medical facility?”

A rose is a rose is a rose, is a silent sentinel and a mainstay for domestic barrier plantings. For security purposes, select roses with strong, woody growth and large thorns, hardy in your area. Climbing varieties can be trained to keep intruders away from climbable downspouts, second-story windows, etc. Bush varieties make beds and fences to keep intruders out, but look homey and wholesome. Photo: J.J. Harrison, via Wikipedia

Many years ago, I energetically bent over a pickup tailgate to lift a heavy box and pushed the back of my jeans into the lower frond of a Century Plant. The hard 1/8-inch spine went through my wallet and impaled one itinerant journalist. This is not to illustrate how thin a scribe’s wallet generally is, but how robust and potentially hazardous thorns on some barrier plants can be.

A few years later, Rich Davis invented the Second Chance vest, a real lifesaver, but on early models reportedly vulnerable to an ice-pick attack. Of course I had to try it, and yes, you could shove a Century Plant tip through a “bulletproof” vest.

Yet Century Plants are a common, attractive and totally acceptable landscape plant to those who live in warmer climates. The edges of the leaves are also lined with smaller curved thorns in such a fashion that if you fall into the plant, you will be cut to shreds getting out.

There is no doubt that some plants can be hazardous to your health if you don’t do things their way, and you can harness that ability for your own home security almost as easily as a packrat builds his nest of cactus shards.


Such passive-aggressive measures as planting barrier plants are worthwhile for the security of your home environs today, no matter what sort of worstcase scenario you may envision for a future time.

Native to Europe, Hawthorn has been used as a barrier plant all over the world for centuries. Shrub or tree depending on how you train it, it has nice flowers and edible fruit and comes in myriad varieties. Photo: © Rasbak, via Wikipedia

Discrete but capable plantings will be more effective in most instances than expensive technology, because they do not attract attention like a row of razor wire that announces, “I am protecting something you probably want.” Unfriendly plants will at least encourage various sociopaths to try their luck somewhere else, with you never even having to engage them in conversation.


Aside from their inherent effectiveness and independence from utility hookups and zoning restrictions, security plantings are socially acceptable, even politically correct. Some municipalities have sponsored seminars on how to effectively use plants for home defense. Historical precedence is on the side of security plantings as well— because they work.

Wild blackberry thickets are called “brambles” in the U.K. and often a “briar patch” in the southern U.S. By whatever name, the old thorned varieties (there are many) provide a barrier and fruit. Photo: Anthony Appleyard, via Wikipedia

Long before technology made modern fencing materials available, anybody with a site to protect knew it was not nice to fool Mother Nature and started from the ground up, with plantings that varied from unfriendly to hazardous.

Virtually every venue offers a local natural selection of unobtrusive yet effective barrier plants, so you’re not limited to Aunt Martha’s heirloom rose bush, as effective as roses can be. Today the selection of proactive barrier plants offers something for every site, in every clime. Most are attractive plants that can be worked into landscaping without even making their defensive potential obvious.

But some, like the wonderfully effective Hardy Orange, are so obviously hostile that when their leaves drop in winter, their purpose can be as apparent as barbed wire.

Hardy Orange, often called the king of barrier plants, is hardy to U.S. Zone 5. The cultivar “Flying Dragon” grows lower, twisted and mean. It’s a common barrier shrub planted around prisons to keep people in, but it also works well keeping people out. This one is at Charles University, Prague. Photo: Karel Jakubec, via Wikipedia
Ocotillo of the arid Southwest has been used for centuries as a living fence or corral. It’s as easy as digging a shallow trench, burying sections, and keeping them watered for a while. Once established, they require no maintenance. They are also an effective and good-looking stand-alone planting. Photo: © David Corby, via Wikipedia
Pyracantha are grown worldwide as a spiny barrier plant or for their white flower and red fruit, which attracts birds. They train up buildings well. Photo: © Laitr Keiows, via Wikipedia


One constant consideration is that the plants be hazardous only to intruders, not to people who belong there. For instance, low plantings in front of windows should be big enough to prevent creeping and loitering, but not so big they can’t be jumped from the inside if used as a fire exit, and not so large as to hide a burglar breaking in that window.

They should not block pathways, just ensure that only authorized pathways are used. They should not present a hazard to invitees such as mail carriers, meter-readers, guests, or emergency medical workers—but such folks seldom loiter under a window, climb a drainpipe, or vault over your back fence.

Many species of Agave exist, and this Agave Americana (aka Century plant) has become naturalized in suitable climes worldwide. A barrier of this is virtually impenetrable by man or beast, but kept pruned and tidy, it’s a handsome (but still impassable) landscape feature. Photo: © Marc Ryckaert, via Wikipedia

Obviously, we don’t want to use barrier plants that may impede normal public access routes or harm innocent passersby. Intruders seek the shadows, but dark areas that might otherwise give them comfortable access can readily be made impassable. Use common sense.

Barrier plants help define boundaries around homes and in gardens. Thoughtful selection and placement of barrier plants are crucial to their effectiveness, but once installed there is scant else as effective.


Consider if plant size will create hiding places and block views. Will the plant prevent your own easy movement? Choose species and locations thoughtfully, and when you can, work with existing structures, such as

plants with barbs and thorns at the base of a privacy fence or along walls or trellises. For hedges, choose defensive plants that are thorny or

One of the prettiest—but meanest—cacti in the business. Native to the American Southwest, Teddy Bear Cholla attaches to whatever brushes against it, giving it the nickname Jumping Cactus. Individual joint breaks off, and the limb often springs back to throw other segments at random.

difficult to walk through and strongly upright.

Whether they are a deterrent or a true barrier depends on species. The hawthorn hedges in France stopped the Allies’ Sherman tanks after the Overlord invasion. Growing a prickly hedgerow and installing a serious gate may be a great combination for eliminating unwelcome visitors in an urban setting. Always plan your access for maintenance.

At a property’s edge, barriers comprising a belt of hawthorn, holly, locust, Hardy Orange, or tightly spaced agave are more than just a “living fence” that draws a line in the sand. And a pair of wire-cutters will not defeat them.

At a property’s center, replace the ivy that climbs a wall (and can aid access to second-story windows or roofs) with good-looking and very thorny pyracantha. Examine your particular property through the eyes of an intruder.

Decide which areas are vulnerable, then plan and plant accordingly. Barrier plants never sleep.

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