Botanical description: Medicago lupulina is an old-world plant found on limestone outcrops and coastal sand dunes. Naturalized across North America from its use as a forage crop for livestock, in the urban environment black medic is most often found along roadsides and compacted walkways. Plants spread only by seed which can remain dormant for years until conditions are conducive for germination. It is relatively aggressive despite its diminutive habit and cute little yellow flowers, tolerating the shade produced by taller, herbaceous vegetation. Individual flowers are found in dense clusters, along trailing stems produced from early May through September. Small clusters of black seed pods follow the blooms, while new flowers continue to be produced further along stems. Leaflets occur in threes and the plant resembles clover in most regards, except for a pointy beak on the tip of each leaflet. Black medic, like other legumes, increases the fertility of the soils it inhabits. Medicago lupulina can fix atmospheric nitrogen into a useable form through a symbiotic relationship with bacterium in the root zone. It has also shown a capacity to uptake heavy metals through its root system and could be used in conditions where phytostabilization is appropriate.