Weld (Span Gualda), a plant, probably native to southern Europe, cultivated as a dyeing material. It is also called dyers' weed, dyers' rocket, and dyers' mignonette. It belongs to the same genus with the garden mignonette, and is reseda luteola. Weld is an erect, stiff, rarely branching -annual or biennial, 1 to 2 ft. high, with linear or lanceolate, entire leaves, 2 to 3 in. long, and yellowish green flowers in long, stiff spikes. It is occasionally found along roadsides in this country, and in England is very common in waste places. Before commercial dyes were so numerous, weld was largely cultivated for the yellow dye yielded by the whole plant, but more especially by the seeds. The seed is sown broadcast, and the next year, when the flowers have opened quite to the top of the spike, the whole plant is pulled and dried. It is used to dye cotton, woollen, silks, and other materials various shades of yellow, and as a basis for a green dye; alum, cream of tartar, and chloride of tin are among the mordants used. The coloring principle is called luteoline; by the action of the air this changes into luteoleine, which crystallizes in golden yellow plates.

The yellow water color called Dutch pink is obtained from weld.

Weld (Eeseda luteola).

Weld (Eeseda luteola).