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Lawn - Moss and Weed Issues

Hi all,

First world problems at the moment and all that but just thought I would reach out to see if anyone has any advice for me in regards to my lawn. 

It was generally okay last summer/autumn but following the seriously rainy period we had over winter and early spring, the lawn has developed a serious issue with moss and weeds. I have attached a few pictures to better describe the problems.  The lawn was laid around three years ago. 

The soil itself was significantly waterlogged and is of a heavy clay consistency which I don’t think has helped the drainage situation that may have contributed to the problem. Clearly the main issue is on the left hand side of the lawn which is relatively shaded by the fencing.  The ground is still very spongy and wet in most places but I have managed one light cut and fertilised the ground using Westland Aftercut Lawn Thickener (Feed and Seed) just once so far this year. 

I do have a decent lawn raker (electric scarifier) and a hollow-tine aerator at my disposal if any of those will help?

Does anyone have any ideas? Thanks in advance of any advice 🙂



  • ObelixxObelixx Posts: 29,854
    You need to improve aeration and thus drainage.   First of all, run over the entire lawn with your scarifier to remove as much loose material as possible.  Then use a good garden fork - or you aerator if it can go deep enough - and pierce the grass regularly and frequently as deep as you can and then wiggle the fork back and forth to enlarge the holes.  Work backwards so you don't compact the soil again by walking on it.

    Then you brush across the lawn some lawn sand - a mix of sharp sand (not builders') and a lawn feed which will sink into those holes and keep them open thus improving drainage and allowing air to get to the roots.   Repeat as necessary every spring and autumn.

    Your grass will look messy for a while but will improve.  Raise the height of the blades on your mower as scalping grass too short will weaken it by reducing the amount of leaf surface that can photosyntesise and make food for good strong roots.

    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • PosyPosy Posts: 3,601
    Both will help, but it would have been better to scarify before seeding because the tines will pull out the young growth. When the ground is drier, I should think you could aerate and brush in grit and compost, but we have some lawn experts in here and I am sure you will get a better answer when one of them noticed your question.
  • Dave HumbyDave Humby Posts: 1,145
    edited March 2020
    Shade and poor drainage are the two biggest contributors to moss and unfortunately it seems you have both. It's obviously difficult to improve the shade aspect and clay soils will always be a problem without extensive drainage efforts. It might be just a case that you accept the conditions and that you'll need to scarify and reseed each spring. You could also lose the lawn to a border in the worst affected area near the fence. That's another option and plant up with some shade tolerant plants and shrubs.

    I'd dig out that couch grass in the bottom right hand of pic three or that will also try and take over. It would also be a good time to apply a selective weed killer if you are not able to hand dig those weed patches out. 
  • JennyJJennyJ Posts: 10,120
    If you can't get sharp sand at the moment, just spiking will let air and water in.
    NB "lawn sand" is a moss killer/fertiliser product. If you use that, it's just sprinkled lightly over the surface, nowhere near as much as you would use for top-dressing/brushing into the holes after spiking. For that you can use plain sharp sand for heavy soil, or a mix of sand and something more water-retentive (traditionally peat and sieved topsoil) for sandy soil. I sometimes empty old container and basket compost on to the grass and brush that in.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • PosyPosy Posts: 3,601
    NOT sharp sand, coarse grit!
  • JennyJJennyJ Posts: 10,120
    I wouldn't use coarse grit - any left on the surface could damage the mower blades (cylinder type here).
    Good lawn care advice here . Of course they're trying to sell their own products but if you ignore that, the advice is sound.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • JennyJJennyJ Posts: 10,120
    On closer inspection of the pictures, I think at least some of the lighter patches are coarse weed grasses (eg in the foreground of the 3rd and 4th pics). They can be a b****r to get rid of. Slashing with a knife weakens them (and one of those hooky weeding knives will tear up some of the root). Otherwise it's a case of dig out, fill the hole with soil and reseed.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • PosyPosy Posts: 3,601
    The point about sharp sand is that it makes clay soil worse. Coarse grit isn't stony and won't affect your mower. 
  • JennyJJennyJ Posts: 10,120
    Even the tiniest of loose stones tend to fly up and ping off my mower blades (other models may behave differently). Some grit once got spilled accidentally on the lawn and it was a pig of a job to get it all off, some got missed and the mower blade got a ding on the edge.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • BorderlineBorderline Posts: 4,700
    On lawns, even clay-base lawns, it is best to stick with sharp sand over coarse grit if given the choice. Of course, first world problems...
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