What is the biggest flaw in my US hemp manufacturing idea? Could this stimulate our economy?

Being that hemp can grow in almost any condition or environment and grows up to 10x faster than trees. Why don't we fill the United States with hemp everywhere and build manf. plants to products top quality lumber, fabric, oil, etc and start exporting and getting some of our money back. It would create countless labor, factory, and commerical jobs. Is what's stopping us the fact that help is considered weed and illegal?