Weed 3 Protection_policy

A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is harmful to agricultural or horticultural crops, natural habitats or ecosystems, or humans or livestock. Most noxious weeds have been introduced into an ecosystem by ignorance, mismanagement, or accident. Some noxious weeds are native, though many localities define them as necessarily being non-native. Typically, they are plants that grow aggressively, multiply quickly without natural controls (such as native herbivores or soil chemistry), and cause adverse effects upon contact or ingestion. Noxious weeds are a major problem in many parts of the world, greatly affecting areas of agriculture, forest management, nature reserves, parks, and other open spaces. Many noxious weeds have come to new regions and countries through contaminated shipments of feed and crop seeds, or have been intentionally introduced as ornamental plants for horticultural use. Some "noxious weeds", such as ragwort, produce copious amounts of nectar, which is valuable for the survival of bees and other pollinators, as well as providing larval host foods and habitats. In the US, wild parsnip Pastinaca sativa, for instance, provides large, tubular stems that some bee species hibernate in, larval food for two different swallowtail butterflies, and other benefits.