Dog lichen (Peltigera sp.)

By | 21/08/2015
Dog Lichen on a Lawn

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?

Dog Lichen
A close up of a patch of dog lichen on a lawn

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.

Kris Lord
The Lawn Man

Further reading:

18 thoughts on “Dog lichen (Peltigera sp.)

  1. Avril Jones

    I have a large lawn about 200 sq meters, last year I had this fungus start, I contacted a university and sent a photo, they suggested I treat it with bicarbonate of soda. I did this took me forever with a watering can. This year it is spreading throughout the whole of the lawn, it is so unsightly, it was a pleasure to find your article online, and to see a picture of it. Now I have a name. Thank you.

    I know you can’t suggest a named product, but If I scarify the whole lawn, then buy the appropriate sand, then treat it with a good lawn feed, should that be ok or can you suggest something else please. I have been so worried not knowing what it was.

    1. Kris Lord Post author

      Hi Avril,
      Thank you for your comment.
      You need to aerate your lawn. The lichen is growing on the lawn because the soil is compacted and dead. Grass will struggle to grow and the lichen will thrive.
      A good hollow-tine aeration treatment will open up the soil and help to bring life back into the lawn. Feeding will also then help. Once fertility has returned, the lichen will be discouraged and fade away.
      A recommend calling your local independant lawn care service to help you to aerate your lawn properly.
      Thanks for reading.

      1. Avril Jones

        Thank you so much for your reply, I have scarified, and aerated, also thrown lawn sand over the lawn, we have mowed it and now have put four in one weed and feed. Today it has poured down, so hopefully the fertiliser will start to work and we can keep an eye on the fungi. I will have my scarifier at the ready , I am determined not to allow it to take over my lawn.

        Thank you very much for your help.

  2. Colin

    Hi Kris, noticed I’ve got this spreading in my front lawn. As a complete gardening novice how and when is the best time to try and get rid of this ?
    Any help on this would be great

    1. Kris Lord Post author

      Hi Colin,
      Dog Lichen grows on poor, neglected lawns. Improve the growing conditions for the grass and the dog lichen will disappear. If you have a bad infestation, it will be easier to physically remove through scarification. Best time to do this is in the spring or autumn. Then overseed, if needed. Continue to feed your lawn through the year and the dog lichen will reduce.
      Thanks for reading

      1. Mary

        Hi Kris
        I’m so glad I’ve found this post.
        We have dog lichen in our garden for about five years and are unable to get rid of it
        We have decided to re lawn but are wondering how we should treat the soil before turfing
        The garden borders are really dry due to neighbors having well established trees and us having a number of bushes.
        Would the lawn benefit if we dug up our bushes and had a full lawn. Colorful plants would probably grow better in pots anyway
        Thank you for any advice you can give

  3. Ann

    So glad I’ve found out what this horrible thing in my lawn is called, will try and irradicate it.

  4. Peter Hunter

    I have had a patch of dog lichen on my lawn for a few years but never knew what is was and it is now spreading. . I have not put any feed on this lawn for years but it is fairly well drained. I am now going to keep it well fed but am wary of scarifying thinking this may help it spread. Am I right or is it ok to scarify?

    1. Kris Lord Post author

      Scarifying won’t usually make it spread, as improving the overall growing conditions for the grass will help to combat it.

      1. Peter Hunter

        Thank you–I have put lawn feed and weed on (containing iron sulphate) and this seems to have helped. I have scarified and am now left with large bare patches which I intend to reseed

  5. Ken Liddell

    Hi, I’ve had a problem with this pest for a few years now. Standard chemicals applied to lawn failed to work, as has been mentioned, however an early “success” was achieved with lawn sand, targeted specifically on the affected patches. At the concentrated level used, much other growth is also suppressed in the target area but grass soon in fills the gaps. Sporulation also means other patches will arise, however these can be managed in a similar way. Ultimately, poor quality soil and poor drainage were the two contributors to creating my particular problem and I have pulled up the turf in the worst affected area and replaced with wild flowers!

  6. Graham Clark

    Thanks for finally giving me a name and cause of this pest which is gradually spreading through my lawns. They are cut regularly but otherwise not much else. (about 2000sq mtrs in all). The site was also previously wooded so I understand the spores, if that is what they are, were probably present all along. The lawn is shaded and poorly drained so I can tick all the boxes.
    I am well out of your area so I will investigate local professionals as a garden fork isn’t going to hack it!

  7. david jones

    I live just outside your area in Appleton and have a big lawn of some 1,600 sq.m. A few years ago I noticed a patch of dog lichen and treated it with concentrated FeSO4. No effect! I’ve had it hollow tined once and have treated it with fertiliser twice each year but it just spreads. It is now about 10% of the lawn surface! I scarify each Spring but this just seems to spread it further as the chopped up bits establish new growth.
    I can hire a spiker, maybe it’s worth buying one and spiking once a quarter then spreading sharp sand to wash in.

  8. Rob Udall

    I am head gardener on an estate in South Derbyshire and have never suffered with this before(dog lichen). At the start of August I noticed a few patches of this stuff on our half acre lawn.We have killed it by aerating and top dressing with a mixture of good sand and seed mix.

  9. James Hyde

    Hi Kris, had a client with this in his lawn, wasn’t sure totally what it was, but your great blog has answered the question.



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