Moss is one of the most common issues in lawns. Over time, in the right conditions, moss will spread and smother a lawn killing it in the process. Moss also acts like a sponge, soaking up water and keeping an area waterlogged and restricting the passage of water through the soil profile. Moss is very different to other lawn weeds and requires a specific treatment; these treatments can be seen below.
For algae and lichen control on hard surfaces please see here