Mosses

(Numerous species) Mosses are found in many places in the garden, but it’s in the lawn that they are mainly regarded as a problem, spoiling its appearance and reducing grass growth.

What is moss?

Although not strictly a weed, mosses are usually regarded as being a “weedy problem”, wherever they grow. But it’s mainly in the lawn that they are seen as a problem, as they out-compete the grasses.

Mosses are simple plants, as opposed to more complex flowering plants. Various moss species can be found in the garden and, depending on species, will grow just about anywhere: in the lawn; on hard surfaces – including paths and paving slabs, furniture and garden structures; on the branches of trees and shrubs; and on the soil. They particularly prefer damp or moist, and often shaded, places.

While they can look attractive, and are often encouraged on hard surfaces to help age them and add to their overall appeal, or as part of Japanese gardens, on paths and patios they can become dangerous slip hazards and lead to nasty falls.

Where do they grow?

Beds
Borders
Lawns
Hard surfaces
Plant stems and branches

Appearance

Various moss species grow in the garden. They either form loose, green or yellowish-green mats or compact, often rounded, cushions.

They produce spore-producing structures, which is how they spread.

How to control moss

There are numerous ways to control mosses, mainly depending on where they are in the garden. Or, they can be left alone, if their presence improves the overall appearance of the structure they’re growing on.

Non-chemical control

On lawns

There are numerous chemical controls and mosskillers that can be used to kill the moss. However, moss is a symptom of poor growing conditions and/or poor lawn maintenance, and unless the underlying problems are corrected, it will just keep coming back. Poor growing conditions include very moist or wet conditions, shade, very acidic or very alkaline soil pH and soil compaction (especially on clay soils). Poor maintenance is usually down to irregular and/or incorrect mowing and a lack of feeding.

Improve the growing conditions for the grass – reducing shade, raking out thatch (dead grass and other debris) and reducing soil compaction by aerating with a hollow-tine aerator and applying a lawn topdressing. Feed the lawn throughout the year to keep the grass growing strongly and help out-compete the moss. And, most importantly, mow regularly to keep the grass at a height of around 4cm (1½in) high all year round, 5cm (2in) or even more in deep shade.

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.

Moss can be controlled to some extent by improving air circulation around and through the plant – prune out any overcrowded branches – especially old branches –and remove vegetation growing around the base of the 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 overly wet 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 with a granular fertiliser. Applying a foliar feed, especially of a seaweed-based tonic, may help to improve strength and vigour.

On hard surfaces

Mosses can usually be controlled by physical removal, such as with a scrubbing brush, or use a pressure washer – although this might just spread them further!

On the soil

Moss growing on the soil is a sign that the soil is compact, airless, may contain too little organic matter and remains moist for much of the year. It is usually only a problem on heavy clay soils.

The moss can be scrapped off, but it 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 and/or horticultural grit.

Chemical control

On lawns

Apply a granular or liquid mosskiller whenever moss is seen. Granular mosskillers are best in spring and autumn, liquid ones in summer. Never rake out moss from the lawn until it is completely dead. If you do, you will just spread the moss and make the problem worse.

On plants

There are no chemical controls for controlling moss growing on plants.

On hard surfaces

Numerous mosskillers for hard surfaces are available. Many are simply watered on and left to work, with no scrubbing or hard work needed.

On the soil

Some mosskillers can be used to treat mosses growing on the soil. They may adversely affect plants, if sprayed onto their foliage, so make sure the spray doesn’t stray.

Use mosskillers safely. Always read the label and product information before use.