Mostly no. Dead leaves that were just lying on a trailer without getting cleaned in advance and bits of decorative plants that broke off are probably the worst offenders.

Worth noting: Plants, living or dead, are banned from Burning Man because they turn into moop really easily, but some always end up there anyway

You think they’re leaving any of that behind?

If it was that'd be an absurd amount of weed being left behind to make a mark on the map.