Posted: 22/01/2015 at 17:10
Siovon......you do need to eradicate the perennial weeds ( bind weed, bramble, dandelion, etc. ) before laying your gravel.
Glyphosate really only works well when you can spray or paint it on the top growth so unfortunately you will need to wait until the weeds are growing and producing enough leaves. With the likes of bramble and bind weed, it may take several applications to totally rid the area.
The advantage of Glyphosate is that it becomes inactive on the actual soil so you can re plant fairly soon after application. The disadvantage is that , as above, one application is unlikely to be sufficient. Best perhaps to start off your Lillies, Hydrangeas, etc. in pots until you know that the baddies have been dealt with.
Weed suppressing membrane is not all it is cracked up to be IME.........if you have any perennial weeds left, they will force their way thru the membrane within a season or two. Also bear in mind that you will still need to do some weeding to remove any annual weeds blown or carried into your garden.
Hope this helps a bit and I wish you all the luck in making some nice borders