Dried coca leaves. The leaves of the coca plant (Erythroxylon coca) contain the stimulant chemical cocaine. The leaves can be chewed to produce a mild stimulant effect, or made into an infusion. The plant is native to the slopes of the Andes in South America, where indigenous people have used the leaves for centuries. The leaves can also be processed to extract pure cocaine, which is an illegal drug in most countries. For this reason the cultivation of the plant is controversial.