Submodule 1: What are invasive weeds?

Establishment and Spread of Invasive Plants

Researchers have divided the process of plant infestation into several steps to help clarify the process.

Introduction and Establishment Phase

Most plant introductions are the result of human activity. While it is possible for plant parts and seeds to travel on wide and water currents, this probably accounts for a very small percentage of actual plant introductions into a new habitat. Fortunately, data collected from several locations around the world has shown that only about 1% of all introduced plants become established and invasive.

 

Environmental factors in a new area influence the ability of a particular plant to become established in its new habitat. While some invasive plants may initially undergo rapid growth, most experience a “lag period” that may last for years or decades. During this time, the new plants may go through some genetic changes that eventually allow them to flourish. This is the time to eradicate the plant – before it reaches the next phase.

 

Rapid Growth Phase

Characteristic of this phase can be explosive growth. It is during this time that many invasive plants are first noticeable in their new habitat. Plants that have more of the characteristics common to invasive plants tend to be the ones more likely to reach this phase of infestation.

 

It is also during this time that invasive plants begin to rapidly reproduce, which is key to their invasiveness and to maintaining their population. They may also be able to establish satellite infestations, depending on environmental conditions and their method of seed or plant part dispersal.

 

Naturalization Phase

Invasive plants that reach this phase are successfully established and able to maintain their population; they have now become part of the flora for the area.