Now is the time to clean them up and get rid of the unsightly and slippery growth. These biological growths thrive in cool damp conditions over winter. ‘Traditional’ herbicides do not affect these growths and some, particularly lichens and nostoc, can be very difficult to get rid of. There are some reports that applying glyphosate may even encourage nostoc growth.
As well as the option of applying SORTED Moss & Mould, Weed Weapon Natural Power is an organic weed killer; it effectively kills annual weeds and young perennial weeds and is also very effective in killing and cleaning the growths on paths and driveways including lichen and nostoc. See the main image above to see how spraying Weed Weapon Natural Power along the edge of a path has cleaned away moss and other growth.