Weld (or Dyer's Weed) is a tall plant with an erect spire up to 5 feet tall of small greenish-yellow flowers with very short petals. It was formerly used to make a yellow dye.
It is similar to Wild Mignonette, except that it is taller, the leaves are strap-shaped (undivided), and the flowers have 4 petals and 20-30 stamens.

Strap-shaped wavy-edged leaves