This week I was called to a lawn which had been infested with a fantastic specimen of Dog lichen (Peltigera sp.), so in this post I will take a closer look at this fascinating, almost alien-looking species which finds its way onto very neglected lawns.
Black slime on my lawn?
Dog lichen is an extremely curious-looking organism. It is very noticeable if a patch manages to find its way onto a lawn. It can find its way onto lawns across the whole of the UK, and the rest of the world.
Dog Lichen looks like a series of grey or black “scales” which spread over the lawn. These scales (called a thallus) have a white underside and can grow to about 3cm across. They swell during wet weather, storing water, and dry out to a thin paper-like thickness in dry conditions.
So what is dog lichen?
It is not a weed, but a lichenised fungi. This means that it is actually two organisms living in symbiosis with each other, and fungus and an algaea covering the fungus. In the case of dog lichen, the algae supplies the fungus with food and the fungus provides the algae somewhere to live and a ready supply of water.
The presence of Dog lichen on a lawn is a sign that the soil is in a very poor state, for it thrives on nutrient-poor soils which are badly drained, compacted and often shaded. It is usually accompanied by a large amount of moss infestation, as mosses thrive in similar conditions.
How does it get on my lawn?
Dog lichen reproduces like a fungus, releasing microscopic spores into the atmosphere which can travel for many miles on the wind. Once they land on a suitable piece of poorly-maintained lawn, if their species of symbiotic bacteria is present, then the lichen will begin to grow.
How do I control dog lichen on my lawn?
Dog lichen is a result of poor growing conditions for grass. As it is not a weed, there are no chemical weed killers which will control it. However, it is not very tolerant to changes in growing conditions, so simply improving the soil will have a dramatic affect and discourage the lichen from growing and spreading.
To improve the soil, aerate the lawn well. This will allow air to penetrate down into the soil and improve the drainage, kick-starting the bacteria growth again. Then brush in a high-quality top-dressing, improving the quality and structure of the underlying soil. A good feed will also benefit the grass, helping it to strengthen and re-populate the affected area.
If you have a problem with dog lichen on your lawn. Please don’t hesitate to get in touch and I will be happy to advise.
The Lawn Man
- RHS Website: Algae, lichens and liverworts on lawns