What natural material that grows on trees?

One natural material that grows on trees is rubber, which is harvested from the latex of rubber trees (Hevea brasiliensis). This latex is collected by making incisions in the bark, allowing the milky substance to flow out and be collected. Rubber is then processed and used in a variety of products, including tires, footwear, and various industrial applications. Another example is cork, which is harvested from the bark of cork oak trees without harming the tree itself.