Melilotus officinalis (yellow sweet clover).
Abstract Melilotus officinalis is a herbaceous legume species, native to parts of Asia and possibly Europe (sources differ on this), that has been extensively introduced to be used as a forage and nitrogen-fixing crop. It has escaped from cultivation and become an invasive weed in many temperate and tropical regions; it can also be toxic to livestock. It is a prolific seeder, and its seeds can remain viable in the soil for many years. It is fast-growing and can grow in a wide range of environmental conditions. Like other nitrogen-fixing legumes, M. officinalis has the potential to alter soil conditions and nutrient cycling. It is allelopathic and so forms dense monospecific stands that displace and inhibit the establishment of native vegetation. In North America, infestations reduce the occurrence of natural fires and degrade native grassland communities that depend on frequent fires. In Alaska and Canada, this species is a serious problem on waterways because it is invading glacial river floodplains. Currently, it is recognized as a conservation problem in North America because it is invading critical natural areas such as national parks and protected lands.