Biennial, US zones 5-9
 
Weld, Reseda luteola, is an ancient dye plant from Europe and North Africa that has been used since the first millennium BCE, and possibly much earlier, to create brilliant and lasting yellows on fiber. Bright greens can be produced when overdyed with indigo or woad. Olive greens and browns are achieved with an iron mordant. 
 
A biennial, weld will make a rosette it's first year, and send up a flowering stalk the next year (though you'll likely get a few the first year as well). Flowering stalks grow 4'-6' adding interest and dimension to the garden, as well as a delicacy for pollinators! This plant needs very little attention, does well in poor soils, and will self seed (though it does not spread quickly in my experience in zone 5). 
 
Direct sow in late summer for flowers in the spring, or in early spring for flowers the next year. Seeds can be started indoors and planted outside after danger of frost. Thin 1'-18". Needs light to germinate.