Varalinth was a type of plant that was native to the planet Vulcan. Its branch roots extended far and wide with them sending shoots upwards that became clones of the parent plant at points wherever the roots approached the surface. They were known to had adapted to the harsh environmental conditions of the Vulcan homeworld by competing heavily with other plants for space. It was this reason why they were at times referred to as weeds.
In 2248, Spock compared his potential experiences with Starfleet Academy as being a veritable garden of different sentients whilst life at the Vulcan Science Academy was more like varalinths. (TOS novel: Crisis on Vulcan)