Alien plants invade many ecosystems worldwide, often having substantia
l negative effects on ecosystem structure and functioning: The apparen
t complexity of invasions has impaired the development of a predictive
framework of alien plant spread. Such a framework requires both a con
ceptual understanding of the ecology of invasions and appropriate mode
lling tools. We demonstrate, using a simple conceptual model and illus
trative examples from the literature, that a predictive understanding
of invasions can be established. Potential modelling tools are reviewe
d by categorizing models of plant spread as either simple-demographic,
spatial-phenomenological or spatial-mechanistic, based on the model's
data inputs and outputs. The assumptions, predictive potential, knowl
edge and data requirements of these modelling tools are discussed in t
he context of selecting the most appropriate alien plant spread model
for a given case.