Question
HAD OUR PATIO INSTALLED ABOUT 2 YEARS AGO AND DID NOT PAY ATTENTION WHEN WE WERE TOLD TO APPLY JOINT LOCK WHICH WOULD KEEP THE WEEDS OUT. NOW WE ARE HAND PULLING THE WEEDS WHICH IS CRAZY.  AM AFRAID TO USE ROUND UP OR SOMETHING LIKE THAN IN CASE IT CAUSES DISCOLORATION.  WHAT CAN YOU RECOMMEND????? HELP PLEASE

Answer
Just bought a big bag of "pre-emergent" granules from Home Depot...Kind of expensive (about $10/pound), but it will keep NEW weeds from forming.  It is a sandy mixture that you can sweep into the cracks of your pavers.  Won't harm tree roots.  I am using it on a driveway to keep the weeds down.  Same issue - concern over staining.

As an aside, I wouldn't worry about round-up discoloring the pavers.  Try it on an inconspicuous corner, forst, if you are unsure.  It will go down "wet", but fade as the chemicals do their magic on these raskles.  ~Marc