Buckwheat (Fagopyrum esculentum) is a plant cultivated for its grain-like seeds, and also used as a cover crop.Despite the name, buckwheat is not related to wheat, as it is not a grass. Instead, buckwheat is related to sorrel, knotweed, and rhubarb. Because its seeds are eaten and rich in complex carbohydrates, it is referred to as a pseudocereal. The cultivation of buckwheat grain declined sharply in the 20th century with the adoption of nitrogen fertilizer that increased the productivity of other staples.