What plant is considered the most useful to humans?

The tree is the most useful, single plant to humans. Not only does it provide a lot of oxygen, but forests are the homes for most of the animals on the planet. Forests are homes to natives of many countries. Natives of America lived among the forests before a different cultured society came along and removed them to make way for towns. Trees are used for our paper, to build buildings, our homes, furniture, and tools.