Crown Vetch Coronilla varia

You will often see crown vetch growing on steep hillsides beside the highway. It is often planted there by highway workman because it grows fast and forms a strong root system, and is therefore excellent at preventing erosion. And, as a member of the pea family, its roots shelter nitrogen-fixing bacteria, which nourish the soil. Its flowers are pink and purple balls, and appear plentifully during most of the summer.