A wildflower (or wild flower) is a flower that grows in the wild, meaning it was not intentionally seeded or planted. The term implies that the plant probably is neither a hybrid nor a selected cultivar that is in any way different from the way it appears in the wild as a native plant, even if it is growing where it would not naturally. In biology, naturalisation (or naturalization) is any process by which a non-native organism spreads into the wild and its reproduction is sufficient to maintain its population. Such populations are said to be naturalised. Some populations do not sustain themselves reproductively, but exist because of continued influx from elsewhere. Such a non-sustaining population, or the individuals within it, are said to be adventive. Cultivated plants are a major source of adventive populations. Naturalised species may become invasive species if they become sufficiently abundant to have an adverse effect on native plants and animals.