Cats go crazy for this easy-to-grow plant. Start early indoors or outdoors after danger of frost. Plant catnip for your favorite feline. This member of the mint family evokes an enthusiastic reaction from most cats. They go wild for it, rolling around and purring and rubbing against the plant. However, it has no scent for humans. A hardy plant that looks similar to mint, it is very easy to grow. In summer, catnip will produce clusters of white flowers accented with purple dots. The leaves are used for teas, but catnip is mostly known for the dramatic effect its scent has on cats.