What do we mean by this?

With the increase in trades between different parts of the globe, the deliberate or fortuitous importation of plant species originating from other more or less distant countries has developed considerably.  Some of these imported plants appear in their wild state, in natural or semi-natural environments.  While many rapidly disappear, others manage to take hold and spread sustainably, reproducing autonomously: we then refer to these as naturalized plants. Some of these naturalized species will proliferate to the point of destroying the balance and smooth running of the ecosystems they colonize or will disrupt certain human activities and even present a risk to public health (poisonous plants): these are invasive exotic plants.

Invasive exotic plants are the plant version of a more general phenomenon, biological invasion, in which all categories of living species may be involved. While biological invasion has no doubt always existed, human activity has doubled its number and frequency.