Acacias are exotics – or non indigenous - to Portugal; in the Peneda-Gerês National Park two species are present, mimosa (Acacia dealbata) and Australian blackwood (Acacia melanoxylon). The mimosa originates from Australia and, in favourable conditions, can reach heights of 20 metres. Its flowers are small, highly aromatic, yellow spheres. It is an invasive species that is well adapted to fires and capable of invading woodlands as well as agricultural land. Acacias grow in such a compact manner that they prevent the growth of other species, resulting in dense thickets that, in themselves, encourage the rapid spread of future fires.