In short
Brown patches on a lawn are most often drought, pet urine, fertiliser scorch, scalping by the mower, or grubs eating the roots. The shape and timing tell you which: irregular patches in a dry spell are drought, round spots with a dark green ring are dog urine, and turf that lifts like a carpet with birds pecking at it is leatherjackets or chafer grubs.
This is a job for my Grass cutting service.
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The most common causes I see on Fenland lawns
Most of the brown lawns I get called to around Wisbech and March in July and August are simply dry. The RHS lists lack of moisture as the usual cause of irregular brown patches in dry weather, worst where tree roots run under the grass or the soil is light and free-draining, and says the grass normally recovers once the rain returns. The silt and sandy patches we get across the Fens dry out fast, so this is the first thing I rule out.
If the patch is small, round and has a ring of darker, lusher grass around it, that is almost always dog urine. The RHS notes female dogs cause it more and that watering the spot straight away dilutes it.
How to tell drought from grubs
Pull on the brown grass. Drought-stressed turf stays rooted. Turf that lifts away with almost no roots underneath has grubs feeding on it. The RHS describes leatherjackets (crane fly larvae) as causing yellowish-brown dead patches from February to October, with crows, magpies and starlings making small round holes in the turf as they dig for them. If you see the birds working a patch, that is your answer.
- Irregular patches, dry summer: drought.
- Round spots, dark ring, near the back door: dog urine.
- Straight stripes after feeding: fertiliser overdose. The RHS says too much scorches the grass.
- Brown on the high spots only: scalping. The mower is set too low for a bumpy lawn.
- Turf lifts, birds pecking: leatherjackets or chafer grubs.
- Patches in wet autumn or winter: fungal disease such as fusarium patch or red thread.
Dry patch: the one that does not recover with rain
Sometimes a patch goes darker green, then brown, and stays brown even after a wet week. Water runs straight off it or sits on top. The RHS calls this dry patch: the soil has become water-repellent, so the grass is in drought whatever the weather. The fix is to spike the area densely and water it daily for several days, and to scarify and aerate in autumn so thatch does not build up again. In bad cases the RHS advises lifting the turf and 8 to 10cm of soil and reseeding.
What I do about it
- Check the cause first. Half the lawns I am asked to treat do not need treating, only time and rain.
- Raise the cutting height in a dry spell. Longer grass shades its own roots and browns far less.
- Never cut more than a third of the blade off at once, and keep the blades sharp so the tips do not tear and brown.
- For grubs, the RHS recommends nematodes applied in September to early October, when the soil is still above 12°C. I can advise on timing for your lawn.
- Overseed bare patches in autumn or spring once the cause is sorted. Seeding a patch while grubs are still in it is wasted money.
If you are in Wisbech, March, Downham Market or King's Lynn and are not sure what you are looking at, send me a photo and I will tell you what I think before you spend anything.