Posted: 21/03/2015 at 22:27
Matthew: Just reinforcing the advice above:
If it's a systemic weedkiller it works by being sprayed onto the leaves of the living plant which then, during the natural process of photosynthesis,* takes the poison down into its roots (ie through its whole system) thus killing the plant literally root and branch.
I am presently clearing a whole border of all planting and weeding as I go; so my ground will be very similar to yours Matthew by the time I've finished.
I know from past experience that missed weed roots will try to regenerate in any bare earth I leave, so I'm covering it all with black porous membrane until I'm ready to plant. Any weeds that actually survive that will be sprayed with systemic weedkiller and then, hopefully, dense planting after that will keep the majority of future weeds at bay - or to a minimum.
* Incidentally, don't cover weeds after spraying them with systemic weedkiller because photosynthesis can't take place if the leaves can't get the sun.