Nitrogen fixation is the conversion of atmospheric nitrogen gas into organic ammonium. Next I want to discuss weeds. A weed by definition depends on the opinion of the one doing the defining. A weed is simply a plant found growing rapidly and abundantly in a place that it is not wanted. From ecological perspective weeds may be regarded as colonizers, plants that are adept at capitalizing on disturbed areas.
Few weeds are actually native to the United States.
Europeans brought many of the weeds with them when they began to colonize this country. They brought the plants they were familiar with like vegetables, herbs, medicinal plants, and garden ornamentals. After spending some time in the New World, native plants were discovered that could serve the same purposes as the ones brought over from Europe. The transplanted species, however, thrived in America, escaping over fences and walls, venturing into the wide-open spaces of the New World. They were then considered to be weeds.