That is actually not so,
unless the state has a specific law restricting items on the Federal list. The Federal laws do not apply to states.
Specifically, Federal laws are only able to limit the interstate transfer of materials -- that's why Colorado can make certain Federally restricted plants legal to possess.
It is illegal to import any Federally listed plant, it is illegal to transport them across state bounds, but otherwise, you can do whatever you want, as long as you don't run afoul of the State's law. In Virginia, for example, the state restricts the sale, trade, or cultivation of any Federally listed plant (e.g., Hygrophila). In Maryland, however, you can do whatever you want with it, there's no law whatsoever restricting it. You just can't bring it across state lines.