A patchy lawn is frustrating — especially when you've tried reseeding and nothing seems to take. The problem is that most homeowners treat the symptom (bare patches) rather than the cause. Scatter seed onto a patch without understanding why it went bare in the first place, and the same thing happens again within a season.
This guide covers the most common causes of patchy lawns in UK gardens, how to identify which one you're dealing with, and what to do about it.
The Most Common Causes of Patchy Lawns in the UK
1. Compacted Soil
Compacted soil is one of the most frequent and least recognised causes of bare patches. In compacted areas, roots can't penetrate deeply, water sits on the surface rather than draining through, and the soil structure becomes too dense for new seeds to establish.
Signs of compaction: water pools after rain, the soil feels hard when you push a screwdriver into it, grass thins gradually in heavily trafficked areas (children's play areas, regular walking routes).
Fix: aerate using a garden fork or hollow-tine aerator before overseeding. This breaks up the compacted layer and gives new roots somewhere to go.
2. Moss Taking Over
Moss is an opportunist. It colonises areas where grass is already weak — in shade, in compacted or acidic soil, or in areas with poor drainage. Once established, moss crowds out grass seedlings and prevents recovery.
Many homeowners rake out moss and immediately reseed. Without addressing the underlying conditions, the moss returns within weeks.
Fix: treat with iron sulphate (liquid application is faster and more even than granular) to suppress moss before any reseeding. Wait for the moss to die back, then overseed into the cleared area.
3. Pest and Grub Damage
Chafer grubs and leatherjackets (crane fly larvae) feed on grass roots from beneath the surface, creating irregular bare patches that appear to die for no obvious reason. A telltale sign: patches of dead grass that pull up easily, or birds repeatedly pecking at specific areas.
Fix: in severe cases, biological nematode treatment applied in late summer targets the larvae. Damaged areas then need overseeding once the infestation is dealt with.
4. Dog Urine
Dog urine contains high concentrations of nitrogen and ammonia which burns grass on contact, creating circular patches — typically yellowed in the centre with darker green around the edges where the diluted nitrogen acts as fertiliser.
Fix: water affected areas heavily immediately after the event to dilute the concentration. For established patches, overseed after the soil has recovered.
5. Shade
Grass requires direct sunlight to photosynthesise. In areas of heavy shade — under trees, against north-facing fences — standard lawn grass varieties simply cannot establish and maintain themselves. Shade patches thin gradually over years.
Fix: use shade-tolerant grass seed blends for affected areas. Manage tree canopies where possible to increase light penetration.
6. Poor Soil Nutrition
Grass that lacks access to the nutrients it needs — particularly nitrogen, phosphorus, and potassium — becomes thin and vulnerable. Thin grass can't outcompete weeds and moss, and the lawn gradually deteriorates into patches.
Fix: pre-seed fertiliser applied before overseeding creates the nutritional environment new grass needs to establish. Standard lawn feeds work for maintenance but don't provide the mycorrhizal support that new seedlings need.
7. Wrong Seed at the Wrong Time
Grass seed applied outside the ideal germination window, at too low a seed rate, or into improperly prepared ground simply doesn't establish. Many homeowners attribute this failure to "poor quality seed" when the seed was adequate but the conditions weren't.
Fix: seed in spring (April–June) or autumn (August–October). Apply at the full recommended rate — undersowing is one of the most common mistakes in lawn repair.
How to Fix a Patchy Lawn — The Right Sequence
The most important thing to understand about patchy lawn repair is that sequence matters. Doing the right things in the wrong order produces poor results.
Step 1: Identify and treat the underlying cause Before anything else, identify which of the causes above applies to your lawn. Treating moss? Apply iron sulphate first. Dealing with compaction? Aerate first.
Step 2: Prepare the surface Scarify lightly to remove thatch and create seed-to-soil contact. Loosen bare patches with a fork. Soil contact is the single biggest factor in germination success.
Step 3: Apply pre-seed fertiliser Feed the soil before you feed the lawn. A pre-seed fertiliser with mycorrhizal inoculant builds the root environment that new seedlings need in their first two weeks.
Step 4: Overseed at full rate Apply UK-specific grass seed at the full recommended rate (35g/m² for overseeding, up to 50g/m² for bare patches). Rake lightly to work seed into the surface.
Step 5: Support new growth Water consistently for the first two weeks. Avoid mowing until new grass reaches 5–6cm.
Not Sure What's Wrong With Your Lawn?
If you're not certain which of these issues is causing your patches, our free lawn diagnosis tool can help. Answer 4 quick questions about your lawn's condition and we'll tell you exactly what's happening and what to do about it.
Take the free lawn diagnosis →
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