The left bag has old stale henna,
the right has fresh henna.
Make sure that your henna supplier sells you fresh henna (which has a light green color, vs. old henna which is more of an dark olive green). Henna can often be found at local whole-health product stores if they sell bulk spices, but I have found that their henna is usually old, stale, and poorly sifted. A better source is your local Indian or Middle Eastern ethnic grocer. These small grocers cater to a community in which henna is part of the culture. Make sure their henna is of decent quality and sealed in air tight pouches. Of course you can also order from on-line dealers. The following links were recommended by Catherine Cartwright Jones.