One whiff and your cats will be hooked. They will not be able to control themselves and will likely wallow your plant to death.  Placing some form of protection around your plants is a good idea.

The leaves are used medicinally to make a calming tea (for people).

Catnip is a bushy perennial that grows two to three feet in height.

Each packet contains 0.25 gram, which is approximately 300 seeds.