What causes moss to grow on soil?

A resilient, rootless plant; moss can grow almost anywhere. It can grow on soil in particular as a result of the soil being moist, airless and compact.
As a species, moss has existed on our planet for millions of years, so it’s no surprise we still find it everywhere, especially in our gardens. From lawns to flower beds - moss growing on soil can be an irritating nemesis for dedicated gardeners and homeowners, as it’s not what you’d call aesthetically pleasing. It’s also a sign of poor growing conditions.

This article will help you understand:

  • What type of moss grows on soil
  • What causes moss to grow on soil
  • How to get rid of moss growing on soil
  • How to stop moss growing on soil 
  • If moss growing on soil is a bad sign

What causes moss to grow on soil?

When moss grows on soil, it’s a sure sign that the soil is moist, airless and compact. Soil used in flower beds, plant pots, rockeries, shrub borders, containers and seed trays is usually the most susceptible to moss growing on its surface. It also tends to thrive in shaded areas. This can include anything shaded by large trees, garages or out buildings, garden walls and fences, or even your house itself.

What type of moss grows on soil?

With over 600 species alone in the UK, the types of mosses that can grow on soil vary. Rhytidiodelphus squarrosus is most commonly the species found in turf or lawns, whereas for compact soils and acid heathland soils, Polytrichum juniperinum may be more prevalent. In particularly wet conditions, Polytrichum commune may present itself. Other types of lawn mosses include:

  • Hypnum
  • Bryum
  • Ceratodon
  • Polytrichum 
  • Eurhynchium

The species has existed on our planet for millions of years, so it’s no surprise we still find it everywhere


Is moss growing in my soil bad?

Moss isn’t directly harmful to plants, as it's a rootless species, so won’t steal the water from your plants and therefore deprive them of their nutrients. However, it can spoil the aesthetic look and feel of the plants you’ve worked hard to maintain.

The only time moss does pose a threat to your landscape is if it grows on your lawn, as it can compete with your grass and cause it to die out. Here are 7 common reasons you might find moss growing on your lawn:

7 reasons you might find moss growing on your lawn


1. Excess moisture

If soil in the lawn becomes soggy due to wet conditions or over-watering - especially clay types - this may drown the grass roots and thus cause it to eventually die. Moss is extremely resilient in wet conditions, and will often thrive in damp, soggy soil due to its shallow-rooted nature. 


2. Too much shade

Even if you’re a seasoned gardener, or only just starting out, no doubt you’ll be familiar with photosynthesis and how grass needs it for healthy growth. But the same can’t be said for moss, which will survive despite the lack of sunlight. It might not be practically possible in some cases (like if a concrete wall is partially blocking the sun from your lawn), but taking steps to reduce shade as much as you can will be a good step towards countering moss growth. Clip and trim trees that inhibit the light reaching your lawn, and reposition garden ornaments and features where you can.


3. Dense clays or soil compaction

When soil becomes too compact, or you use a particularly dense clay on your lawn, the grass may struggle to grow. Grass is a robust plant, and can often grow through heavy top soils. But it has its limits, whereas soil is far more resilient and can easily thrive on compact clay or soil.


4. Dry soil

Moss thrives in overly moist conditions, so surely dry soil wouldn’t present a problem? You’d think as much, but the problem is soil shrinks if it loses moisture, which in turn makes it denser. This damages the grass roots, depriving them of water and much needed nutrients, which is why extra needed care is needed in the summer months. However, when the moisture reappears through rain or through your hosepipe, moss seizes its opportunity to compete with the grass, as its spores easily germinate. So keep checking your soil in the heat to make sure it isn’t drying out.


5. Tree Roots

Tree roots are strong, and after years of solid growth they may have spread through the soil underneath your lawn. In some cases this can deprive the grassroots from burying into soil and absorbing the moisture they need to grow. This allows moss to grow on the tree roots. Another way tree roots may cause moss on your lawn is if the lawn isn’t watered enough. When this happens, the microscopic feeder roots of the tree can compete with the grass for moisture. This grass can become damaged or weakened as the feeder roots compete with it, allowing for moss to enter the environment and thrive. 


6. Poor lawn care

Inadequate mowing or lawn trimming can cause moss production. Cut your grass too short, in an act us gardners call ‘scalping’, and the grass won’t survive. The same goes for slight trimming to neaten grass that’s close to the ground. It may look aesthetically pleasing, but short grass can’t photosynthesise and will likely die. This opens the door for moss to thrive in its place. So don’t get over keen and be mindful of how short you cut your grass. Also consider weighing up aesthetics over moss invasion. We all want our gardens to look nice, but making them too perfect may result in moss growing on soil.


7. Over acidity of soil

If soil is too acidic or alkaline, the nutrients within it protect themselves and won’t be released to feed your grass. A lack of nutrients will inevitably lead to unhealthy or even dead grass, again paving the way for moss to run rampant.

How do I get rid of moss growing in my soil?

If you don’t want to use a weed killer, then scarification can remove moss from soil. You can do this with a hoe, rake or small trowel, taking care not to damage the grass or plants. There are non-chemical products you can use that not only control the moss, but also break it down while it’s dead, saving you the time and effort of scarifying the dead moss from your lawn.

Like others are you wondering can you compost moss? Read the blog and find out.

3 ways to stop moss growing on my soil?

1. Maintain soil acidity

One way of controlling moss growing in soil for the long term is monitoring and maintaining the acidity levels in the soil. If you haven’t got one already, get a testing kit from a garden centre which you can use to check the soil’s acidity, which should ideally be as close to neutral (pH 7.0.) as possible.

2. Prevent soil compaction

To deter soil compaction, especially after heavy rain, mix manure, compost, processed bark or leafmould into the soil to increase its organic content.

3. Mulch the soil

In rockeries and containers, mulch the soil with grit, gravel or slate to prevent the soil from becoming compacted or impoverished, which will stimulate unwanted soil growth.


Thank you for reading I hope you have found this blog post interesting and you now know what causes moss to grow on soil?