[green bean]

I was told I can add perrenial weeds to my compost if I leave it for 3 years to rot. Is this true.

[Yorkie]

You could try, but it will partly depend I think on how hot your heap gets - whether they just carry on growing or decompose 

I never have compost hanging around for 3 years, and don't want to run the risk either, so don't bother.

[arugula]

You can burn them on a bonfire and use the ash direct on the ground or put it in the compost.

[sunshineband]

Or soak them in water until the begin to rot and put them (and water) onto the compost... they don't grow then 

[fatbelly]

Or just make sure that the seed has and roots on not composted.
Just compost the green leaves and stork of the weed.