A cactus fence is a hedge

Hedge (gardening)

A hedge or hedgerow is a line of closely spaced shrubs and tree species, planted and trained in such a way as to form a barrier or to mark the boundary of an area. Hedges used to separate a road from adjoining fields or one field from another, and of sufficient age to incorporate larger trees, are...

 or fence

Fence

A fence is a freestanding structure designed to restrict or prevent movement across a boundary. It is generally distinguished from a wall by the lightness of its construction: a wall is usually restricted to such barriers made from solid brick or concrete, blocking vision as well as passage .Fences...

 made of closely spaced cactus

Cactus

A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

 plants, sometimes with barbed wire

Barbed wire

Barbed wire, also known as barb wire , is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand. It is used to construct inexpensive fences and is used atop walls surrounding secured property...

 or wood interwoven with the cacti.

Such fences are inexpensive to develop in regions where cacti are common, and can provide an extreme deterrent to any but a determined human intruder

Intruder

- Film and television :* Intruder , a horror movie from 1989.* Intruder , a film by Vicente Aranda.* The Intruder , a film by Albert Ray.* The Intruder , a film by Guy Hamilton...

. Often their primary function is to keep wandering large animals off a private property.

Sometimes, cacti are used as barriers without being formed into a structured fence. Prickly pears

Opuntia

Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...

 (mostly Opuntia stricta

Opuntia stricta

Opuntia stricta is a species of cactus from southern North America, Central America, the Caribbean, and northern South America. Common names include Erect Prickly Pear and Nopal Estricto ....

) were imported into Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 in the 19th century for use as a natural agricultural fence and to establish a cochineal

Cochineal

The cochineal is a scale insect in the suborder Sternorrhyncha, from which the crimson-colour dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America and Mexico, this insect lives on cacti from the genus Opuntia, feeding on plant moisture and...

 dye

Carmine

Carmine , also called Crimson Lake, Cochineal, Natural Red #4, C.I. 75470, or E120, is a pigment of a bright-red color obtained from the aluminum salt of carminic acid, which is produced by some scale insects, such as the cochineal beetle and the Polish cochineal, and is used as a general term for...

 industry, but quickly became a widespread weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

.

In the American southwest

Southwestern United States

The Southwestern United States is a region defined in different ways by different sources. Broad definitions include nearly a quarter of the United States, including Arizona, California, Colorado, Nevada, New Mexico, Oklahoma, Texas and Utah...

, ocotillo

Ocotillo

Fouquieria splendens Engelm. is a desert plant of the southwestern United States and northern Mexico. Common names include ocotillo, desert coral, coachwhip, Jacob's staff, and vine cactus, although it is not a true cactus...

stems are often set in the ground to form a structure similar to a cactus fence.