Posted: 17/07/2013 at 11:40
Glyphosate will do the job, but you have to give it time. You should spray it on the leaves then wait for the leaves to die down completely (up to 6 weeks.) If you remove the foliage before then, the roots may not be killed and you then have to wait for the leaves to grow again, spray, then wait another few weeks for them to die down. If you can't dig the roots out, then you have to wait for the glyphosate to work fully.
If you are desperate to get the new plants in, then do so and label them all. If anything comes up which isn't labelled, apply a glyphosate gel directly to the leaves instead of spraying so that you don't damage the new plants.