Escaped plant

[5] Plants may escape from cultivation in various ways, including the dumping of green waste in bushland and road reserves and by birds or other animals eating the fruits or seeds and dispersing them.

[10] Some plants, such as the opium poppy Papaver somniferum,[11]: 93  escaped from cultivation so long ago that they are considered archaeophytes, and their original source may be obscure.

Further, ornamental alien plants can easily escape their confined areas (such as gardens and greenhouses) and naturalize if the climate outside changes to their benefit.

For example, species of Opuntia (prickly pears) have been introduced from America to Australia, and have become wild, thus rendering territories unsuitable for breeding[clarification needed]; the same goes for European gorse (Ulex europaeus) in New Zealand.

Robinia pseudoacacia was imported from America to Central Europe for its rapid growth, and it now threatens the scarce steppe and natural forest areas of the drylands.

In nutrient-poor heaths, but rich in grasses and bushes (fynbos) in the region Cape in South Africa, species of eucalyptus from Australia are growing strongly.

As they are largely accustomed to poor soils, and in the Cape region they lack competitors for nutrients and parasites that could regulate their population, they are able to greatly modify the biotope.