It's important to read the seed label before purchasing. Inert material is something you'll see on the tag; here's why you should avoid it.

Perhaps one of the most surprising discoveries of the 20th century was that this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe. The rest of the universe ...

A woman chooses a packet of seeds from the selection hanging on the shelves in a garden center. - Juan Reig Peiro/Getty Images ...