Reseda luteola

Reseda luteola is a flowering plant species in the family Resedaceae. Common names include dyer's rocket, dyer's weed, weld, woold, and yellow weed. A native of Europe and Western Asia, the plant can also be found in North America as an introduced species and common weed. While other resedas were used for the purpose, this species was the most widely used source of the natural dye known as weld. The plant is rich in luteolin, a flavonoid which produces a bright yellow dye. The yellow could be mixed with the blue from woad (Isatis tinctoria) to produce greens such as Lincoln green....read more on Wikipedia.