Legumes are plants with flowers like the sweet pea and produce their seeds in pods.
Compared to grasses which have long slender leaves, legumes have compound leaves with three or more broad, rounded leaflets. Most legumes have tap roots which are able to obtain water from deeper in the soil than the roots of grasses. Legumes are highly valued because they are rich in protein and yield well without being fertilized with nitrogen. This is because legumes are able to form a mutually beneficial relationship with Rhizobia bacteria. In this association, the bacteria, which live in nodules or swellings on the legume roots, are able to fix atmospheric nitrogen and make it available to their host plant.