The Barb-wire Bush is a genetic construct designed for use in low-tech entrenched fortifications, kind of like the West Front in the first world war of Old Earth. The plant consists of a central mass of roots, from which radiates a multitude of ground-hugging vines. Those vines have an incredible tensile strength and are studded with 10-centimetre, razor-sharp barbs (which in some breeds are poisonous).
The purpose of the plant is to inhibit a person trying to traverse the area on foot, tangling eir clothes, and shredding every spot of bare skin they can find. If the person stumbles and falls, e definitely won't get up again without assistance. Because they are so resistant to large herbivores, barb-wire Bushes tend to be the last things to mark old battle-fields; sometimes they prevailing for hundreds of years after the war in which they were seeded ended.
The most common use for such plants in civil settings is as a low cost privacy and security measure. Such versions may be designed to be as aesthetically pleasing as they are impenetrable.