Liverworts are small plants related to, and often confused with, mosses. They are generally harmless in the garden – and some people actually encourage them, as they make structures, ornaments and containers look aged and distinguished.
Liverworts are green growths found in various places in the garden – mainly on the soil and hard surfaces, although they can also grow on plants, where they do no harm. There are two main types – those that have a flat, plate-like body and those that produce flattened ‘leaves’.
They usually need moist, damp or even wet conditions to thrive in, and somewhere that doesn't get strong, direct sunlight. In fact, the same conditions that mosses prefer and thrive in.
When liverworts are found growing on trees or shrubs, this is usually a symptom that the plant is already either weak or stressed. It could simply be that it is old and getting ‘past its best’, or has already begun to die back because of some other problem.
When growing on paths, paving and patios, they can make the surface very slippery.
TREATMENT AND CONTROL
There are no chemical controls for liverworts growing on plants. You could try to physically remove it, but this should be avoided as it would probably do more damage to the bark and branches.
Liverworts can be controlled to some extent by improving air circulation around the plant – prune out any overcrowded branches and remove excess vegetation growing around the affected plant.
Improve the overall growing conditions for the plant to improve its strength. Look at the condition of the soil and whether it becomes too dry in summer or waterlogged. Ensuring conditions for good root growth will help to increase the plant's vigour. Water if and when necessary, mulch the soil and feed annually in spring. Applying a foliar feed, especially of a seaweed-based tonic, may help to improve strength and vigour.
ON THE SOIL
Liverworts growing on the soil is a sign that the soil is compact, airless and remains moist for much of the year. They are usually only seen on heavy clay soils.
They can be scrapped off, but will return unless something is done to improve the compaction and drainage of the soil. Dig over the soil and dig in bulky organic matter and even sharp sand or horticultural grit.
ON HARD SURFACES
Liverworts can usually be controlled by physical removal, such as with a scrubbing brush, or by treating with a patio cleaner. On pots and containers, only physical removal is suitable.