Forest plantations tend to be the source of propagules if tree species become invasive. Such plantations in the part of southern Australia with a mediterraneantype climate are largely of pines, especially Pinus radiata. There is a smaller component of Pinus pinaster, particularly on soils of low fertility in south-west Western Australia. Small trial plots have been established in arboreta of many other species in the genus, especially P. laricio, P. ponderosa, P. contorta, P. muricata, P. halepensis, and some other coniferous genera such as Cupressus.

Forest plantations of these species have been established principally on sites which formerly carried tall open-forest or open-woodland (Specht, 1970), inwhich Eucalyptus species were the main trees, and species of Acacia (either shrubs or small trees) were associated species. After establishment it has usually been necessary to remove regrowth of the indigenous species, either as coppice shoots from stumps, as regenerated seedlings, or as root suckers in the case of some Acacia species, to ensure establishment of the pines. Such persistent plants are often referred to as ‘woody weeds’, although in no way do they possess invasive characteristics.

At a rotation age of about 30 to 40 years, the pine stand is typically without associated species, either indigenous or introduced, except for a few lowgrowing herbs on the forest floor and some bryophytes on wetter sites. Occasionally, in moist localities, European blackberry (Rubus spp.) may enter the stand and persist as an undesirable species in the management system.