The Plant Edit
Onions have been cultivated for more than 3000 years. Plants produce flattened-globose bulbs covered in papery skins and star-shaped flowers. Onions prefer medium to light soils and do not produce heavy crops in sand, chalk, or clay soils. Roots and leaves are formed when daylight does not exceed 15-16 hours and bulb scales are produced during longer summer days.  Grocery stores and farmers markets often have onion skins as a waste product and are a potential source for dyers. 
How to Harvest Edit
Dye is extracted from the papery skin, the tunic, on the exterior of the onion bulb. Because skins weigh so little, a large amount of skins is required for dyeing. Thoroughly dry skins can be stored in a paper bag until enough have been saved to dye with.  However, grocery stores and farmers markets often have onion skins as a waste product and are a potential source for dyers. 
How to Extract Color Edit
Onion skins can be used to obtain a vibrant color with or without a mordant.  Without a mordant, the color may not be entirely light-fast. A strong bath can be produced using twice the weight of onion skins to the amount of fiber and will produce a brown or brown-pink without mordant. A strong bath with alum or tin will produce an orange, chrome will produce orange-tan, and copper will produce a darker brown. A bath 1/5th as strong will produce pale yellow without mordant, bright yellow with alum, yellow-orange with tin, khaki with chrome, and brown with copper. Onion skins can leave a strong smell in fibers that takes several washings to remove. Red or purple onion skins may produce a slightly different color from yellow-brown onion skins 
- ↑ 1.0 1.1 1.2 Cannon, J., & Cannon, M. (1994). Dye plants and dyeing. Portland, Or.: Timber Press.
- ↑ 2.0 2.1 2.2 Duerr, S. (2010). The handbook of natural plant dyes: Personalize your craft with organic colors from acorns, blackberries, coffee, and other everyday ingredients. Portland, Or.: Timber Press.