Melilotus officinalis

It is a biennial legume native to Eurasia that is now widespread in North America. It is valued for its use as a cover crop, forage, and for attracting pollinators, but it can also be an aggressive invasive weed that degrades native habitats. The plant contains coumarin, which can be converted to a toxic compound in poorly cured hay, leading to sweetclover poisoning in livestock. Leaves alternate on the stem and possess three leaflets. Yellow flowers bloom in spring and summer and produce fruit in pods typically containing one seed. Seeds can be viable for up to 30 years. Plants have large taproots and tend to grow in groups. Plants have a characteristic sweet odor. The sweet hay-like aroma of the foliage is caused by coumarin. It is considered an invasive weed because it outcompetes native plants for resources.