Renovating An Old Flower Bed.
To renovate an old flower bed thats full of weeks especially perennial weeds it worth taking you time.First roughly dig or fork it over as best you can and break up the soil.Next apply a mulch or a covering of compost such as spent mushroom compost or farm yard manure.It worth noting how many lob worms you come across then digging the bed over,if its less than 3 a square metre then its worth adding a few extra ones.
As the perennial weeds such as couch grass and the dock type weeds with tap roots start to recover and send up new shoot, treat the bed with Round up weed killer. Best to use an old watering can or a watering can just for this purpose.
It likely that to get the perennial weeds under control it will take 3 to 4 treatments but its time well spend.