Bur

A bur (also spelled burr)[1] is a seed or dry fruit or infructescence that has hooks or teeth.

[4] Containing seeds, burs spread through catching on the fur of passing animals (epizoochory) or machinery as well as by being transported together with water, gravel and grain.

[6] It also might penetrate a hoof or foot pad or the tires of a vehicle, only to be shed after being carried for a considerable time and distance; most Tribulus and Grielum species are specialised for such attachment, variously being flat, but with upward-directed spikes as in say, Grielum humifusum,[7] or shaped like a caltrop as in some species of Tribulus that have achieved the status of cosmopolitan weeds by sticking to the tires of aircraft.

[4] Burs are best known as sources of irritation, injury to livestock,[2] damage to clothing, punctures to tires, and clogging equipment such as agricultural harvesting machinery.

Furthermore, because of their ability to compete with crops over moisture and nutrition, bur plants can be labelled as weeds and therefore also be subject to removal.