Allelopathy: The process by which organisms release chemical compounds known as ALLELOCHEMICALS which influence the physiology, growth, survival, colonization, and reproductive activities of other species usually located nearby.Echinochloa: A plant genus of the family POACEAE that is grown mainly as a hay crop.Comfrey: Perennial herb Symphytum officinale, in the family Boraginaceae, used topically for wound healing. It contains ALLANTOIN, carotene, essential oils (OILS, VOLATILE); GLYCOSIDES; mucilage, resin, SAPONINS; TANNINS; triterpenoids, VITAMIN B12, and ZINC. Comfrey also contains PYRROLIZIDINE ALKALOIDS and is hepatotoxic if ingested.Mucuna: A plant genus of the family FABACEAE that is the source of mucuna gum.Vicia: A plant genus of the family FABACEAE that is widely used as ground cover and forage and known for the edible beans, VICIA FABA.Polygonum: A plant genus of the family POLYGONACEAE that is an ingredient of Shou-Wu-Pian, a Chinese herbal preparation (DRUGS, CHINESE HERBAL). The common name of black bindweed also refers to TAMUS or Fallopia (use POLYGONACEAE).Poa: A plant genus of the family POACEAE that contains the Poa p Ia allergen and allergen C KBGP.Geranium: A plant genus of the family GERANIACEAE. Geranium is also used as a common name for PELARGONIUM.Centaurea: A plant genus of the family ASTERACEAE. Members contain 5-methyl-8-hydroxycoumarin. The common name of centaury is more often used for CENTAURIUMEutrophication: The enrichment of a terrestrial or aquatic ECOSYSTEM by the addition of nutrients, especially nitrogen and phosphorus, that results in a superabundant growth of plants, ALGAE, or other primary producers. It can be a natural process or result from human activity such as agriculture runoff or sewage pollution. In aquatic ecosystems, an increase in the algae population is termed an algal bloom.Plant Weeds: A plant growing in a location where it is not wanted, often competing with cultivated plants.Pheromones: Chemical substances, excreted by an organism into the environment, that elicit behavioral or physiological responses from other organisms of the same species. Perception of these chemical signals may be olfactory or by contact.Lettuce: Any of the various plants of the genus Lactuca, especially L. sativa, cultivated for its edible leaves. (From American Heritage Dictionary, 2d ed)Rhizome: Root-like underground horizontal stem of plants that produces shoots above and roots below. Distinguished from true roots which don't have buds and nodes. Similar to true roots in being underground and thickened by storage deposits.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.