There is No Natural Black Henna powder.
However, the only plants that give black color dye naturally are: The Indigo which can be found in India under the name of Indigofera tinctoria, the Chinese Indigo Baphicacanthus cusia, and the Katam plant Buxus dioica. However, Indigo can cause some itching in some rare cases. Most Black Henna products in the market are unfortunately made from synthetic dyes and chemicals which have been reported dangerous for skin inscription and for hair application. Since there are a lot of brands in the market, and many of them contain highly risky and unsafe chemicals, we recommend everyone to do a proper research about the brand before purchasing any Henna powder in order to avoid harmful consequences.