I also use pva foam all year, regardless of weed levels, leaves, whatever; even if I'm fishing on hard gravel. It helps separate the hook bait from the lead on the cast, improves presentation for any rigs with a degree of stiffness, just helps in every department IMO. I will adjust the way I attach the foam in cold water (I've seen the foam stay on all night before!).
Once it's on the deck I actually agree with Phil - Dead leaves are so forgiving as a substrate, same as silt; we worry about presentation but the carp will find a way if they're feeding. I'd happily fish a bottom bait over leaves if forced to (normally use pop ups anyway though).
Useless fact time: the foam stuff is actually not pva, it's corn starch based, just called pva so anglers get the point of what it is.