Moss, bare earth, yellow spots and thin, weedy grass are the lawn problems we are asked about most. It is tempting to reach for a bag of moss killer or a box of seed, and sometimes that is all it takes. More often, though, the same problem comes back year after year because the reason behind it has not changed.
Below are the common causes we see in South Wales gardens, how to recognise each one, and what tends to fix it. When a lawn is past saving, our turf laying service can give you a fresh start on properly prepared ground.
Moss: a sign, not the cause
Moss thrives where grass is struggling. It likes damp, shade, compacted or poorly drained soil, acidic ground and grass that is cut too short. With our wet winters and the many gardens shaded by valley sides, walls or trees, it is no surprise that moss is the most common lawn complaint in the area.
A moss killer, usually based on iron sulphate, will blacken the moss and it can then be raked out. But unless the conditions change, it will be back. Lasting improvement comes from letting in light, relieving compaction, improving drainage and raising the mowing height so the grass can outcompete it.
Wet ground and compaction
Heavy clay soils, common across much of South Wales, hold water and pack down easily. Once compacted, air cannot reach the roots, water sits on the surface and the grass thins, leaving room for moss and weeds. Well-trodden routes across the lawn, such as the path to the shed or washing line, suffer most.
New-build gardens are especially prone to this. The ground has often been driven over by machinery, then covered with a thin skim of topsoil and turf, so there is a hard, airless layer only a short way down. The lawn may look fine for a year or so, then turn wet, thin and mossy. Breaking up that layer properly usually means lifting the lawn and starting again.
- Aerate each autumn with a fork or hollow-tine aerator, then brush in a sandy topdressing.
- Put stepping stones or a paved path along the routes people always walk.
- Stay off the lawn when it is waterlogged.
- Where water lies for days, a land drain or soakaway may be needed. Our guide on stopping a garden waterlogging explains the options.
Shade from trees, fences and buildings
Grass needs light. Under a spreading tree, along the north side of a fence or in the narrow strip beside a house, it grows thin and weak, and moss moves in. Trees add to the problem by taking water and nutrients, and their falling leaves smother the grass in autumn.
Options include thinning or lifting the crown of a tree to let more light through, overseeding with a shade-tolerant mix, and raising the height of cut in shaded areas. Where the shade is deep, it is often better to accept that grass will not thrive and plant a shade-loving border or lay bark or paving instead. Our tree surgery team can advise on what can be done with the trees.
Bare patches: the usual suspects
- Heavy wear: goalmouths, swings and trampolines. Move them around, or reseed and rest the area.
- Dog urine: yellow or brown patches, often with a ring of dark green grass. Watering the spot straight after helps dilute it.
- Scalping: bumps or ridges cut too low by the mower. Raise the blades, and level hollows and humps with topdressing over time.
- Things left on the grass: a paddling pool, a plank or a pile of leaves for a week can kill the grass underneath.
- Spills: fuel, oil, weedkiller or too much fertiliser in one spot can scorch the grass.
- Buried rubble: grass over hidden brick or concrete dries out and browns first in summer.
Grubs and digging animals
If patches of grass turn yellow and can be lifted like a loose carpet, with no roots holding them, the roots may have been eaten by grubs in the soil. Leatherjackets, the larvae of crane flies, and chafer grubs are the usual culprits. Often the first sign is birds, foxes or badgers tearing up the lawn to get at them.
Pull back a section of affected turf and look in the top few centimetres of soil. Biological controls using nematodes are available for some lawn grubs, applied at particular times of year when the soil is warm and moist. Once the grubs are under control, the damaged area can be repaired with seed or new turf.
Weeds, poor soil and hungry grass
A lawn full of clover, moss and small weeds is often simply hungry. Grass that is never fed gradually thins, and plants that cope with poor soil take over. Red thread, a common disease that leaves pink or reddish patches, is also more frequent on lawns short of nitrogen.
Regular feeding in spring and autumn, sensible mowing and the odd dose of selective weedkiller usually turn this round within a season or two. Our guide on looking after a lawn through the year sets out a simple routine.
Repair, renovate or start again?
If the lawn is mostly grass with some problem areas, renovation is usually the answer: scarify, aerate, topdress, overseed and fix whatever caused the damage. Small bare patches can be cut out and replaced with pieces of turf, or reseeded.
If the lawn is mostly moss, weeds or bare soil, has lumps and hollows, or sits on badly drained ground, it is often quicker and more satisfying to start over. That means clearing it, sorting the soil and drainage, and laying new turf, as described in our guide to preparing ground for turf.
Tony and the team can take a look, tell you honestly whether your lawn is worth renovating, and give you a free quote for either route. We work across the region, from Pontypool and Cwmbran to Port Talbot.
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Questions People Ask
Why does moss keep coming back after I treat it?
Because moss killer only removes the moss, not the conditions it likes. Unless shade, compaction, poor drainage or short mowing are dealt with, the moss returns within a season or two.
Will grass grow back on its own in bare patches?
Small patches may fill in from the edges in the growing season. Larger ones usually need help, either seed sown into loosened soil or a piece of turf cut to fit.
Is lime good for a mossy lawn?
Only if the soil is genuinely very acidic, and many lawns are not. Test the soil first with a simple kit. Adding lime without need can encourage weeds and other problems.
What are the brown patches that appear in summer?
Often drought stress, especially over thin soil or buried rubble. Grubs, dog urine and scalping can look similar, so check whether the roots are intact and whether the patch lifts easily.
Can a waterlogged lawn be fixed without re-turfing?
Sometimes. Aerating and topdressing help mild cases. Where water lies for days, drainage work is usually needed, and it is often easiest to do that and re-turf at the same time.