Algae and algae-like growths  

Algae thrive in wet conditions, and their growth is faster in shady areas with poor air circulation.  

• A green film or powdery deposit of algae may be seen in sparse, bare patches of lawn. 
• Algae-like Nostoc form greenish-brown, jelly-like growths when wet, which become dark and crusty when dry. Nostoc grow in damp areas of lawn.

Lichens 

Peltigera (dog lichens) are the most common type of lichens in lawns. They can be brown, grey or green and form flattish structures that grow over turf. When dry, they become crusty and often lighter in colour.

Liverworts 

Liverworts in lawns usually have a green, flattened body and no leaves. They thrive in damp, compacted soils in shady areas.

Not necessarily – a species-rich lawn increases the biodiversity of your garden and even a small patch of lawn can support many native species of algae, lichens and liverworts.

However, they can create slippery patches, so as a safety measure, it is advisable to prevent or manage their growth on areas of lawn that are walked on. They can also compete with, and potentially smother, lawn grasses – though their presence indicates that growing conditions aren’t ideal for a lawn and the grass species are likely to be struggling anyway.

If you want to rid your lawn of algae, lichens and liverworts, the best approach is to adjust the growing conditions to discourage them, and at the same time encourage dense, healthy turf. There are several ways to achieve this:  

• Aerate and top dress your lawn to relieve compaction, improve drainage and stimulate grass growth. See our guide to autumn lawn maintenance for more advice. 
• Reduce compaction by staying off the lawn when it is wet, particularly on heavy clay soil.  
• Reduce shading to make conditions less favourable for algae, Nostoc, liverworts and some lichen species. Remove lower branches from nearby trees and shrubs, or thin out their canopies to allow more light onto the soil surface and improve air flow.  
• Install drainage where your lawn is regularly saturated, but bear in mind this is a major task and finding somewhere suitable for surplus water to be diverted to can be challenging. For more information, see our pages on waterlogging and flooding and installing drainage.  
• Remove the lawn and replace it with plants better suited to the growing conditions, such as shade- and moisture-loving ground cover plants.

Aerating with a border fork is suitable for small areas

Top dressing after aerating improves drainage 

Re-seed resulting bare patches with a shady lawn mix in spring or autumn, following advice in our guide to repairing lawns. However, bear in mind that if drainage isn’t improved, it is likely that growths will return.