Posted: 18/04/2012 at 00:39
They are persistant aren't they ! I have a couple of raised beds which I covered during the winter to stop weeds and when I removed the covers a few weeks ago there was nothing but sycamore seedlings. Thankfully they were easily enough removed. I don't have an answer to the OP's question other than to watch out for the seeds in summer when weeding, etc, because they seem to "come down" well before autumn especially after a windy day/night. But this may not be practical if you have a medium/large garden.