Weeds

A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.The term "weed" has no botanical significance, because a plant that is a weed in one context, is not a weed when growing in a situation where it is wanted.

Although whether a plant is a weed depends on context, plants commonly defined as weeds broadly share biological characteristics that allow them to thrive in disturbed environments and to be particularly difficult to destroy or eradicate.

(excerpted from Wikipedia)