Silvervine is a natural, non-toxic herb grown in China and Japan. Matatabi is the Asian name.
It's a different plant to catnip, but produces similar results in cats! Many, but not all, cats love to roll around in scattered Silvervine, chew on it, play with it, and generally have fun!
Not all cats react to catnip (it's thought around a third do not) - these cats may well react to Silvervine (though it's not guaranteed) and lots of cats who do like catnip will also like Silvervine too! Just like ours in fact!
You can use it to re-generate cat toys (i.e 'marinate' the toy with some leaves for a while), or just sprinkle it on the floor if you don't mind a bit of mess!
They will keep your kitties happy for quite a while! Just remember to keep the container/bag tightly closed and put away somewhere safe when finished with, otherwise you may find little paws and teeth have opened it :)