Brown Patches in the Lawn: Find the Cause and Fix It Properly

Cause first, then repair

Brown patches all look alike but have very different causes. If you just overseed without knowing why, the patches will be back next year. These three tests take five minutes in total:

1. Tug test: Pull hard on the grass where brown meets green. If the turf lifts like a loose carpet, the roots are gone, which is typical of grubs.
2. Screwdriver test: Push a long screwdriver into the soil. If it barely goes in, the soil is dried out or heavily compacted.
3. Shape check: Round patches with a dark green edge? Stripes or patterns? Growing circles with a coating? The shape tells you a lot.

The most common causes at a glance

Sign	Likely cause	What helps
large straw-coloured areas, hard soil	drought	water deeply, grass often recovers
round patches with a lush green ring	dog urine	water at once, overseed
turf lifts off, birds pecking	grubs	nematodes, then overseed
stripes or patterns after feeding	fertiliser scorch	water heavily, spread evenly
thick, spongy thatch, moss	thatch / compaction	scarify, aerate
round patches with a reddish or white coating	fungus (e.g. red thread, snow mould)	potassium feed, aeration, clear leaves

Case 1: Drought

In hot summers lawns often turn brown over large areas, especially on south-facing sides, sandy soil and above pipes or stones. The good news: the grass is usually just dormant. Water rarely and heavily (10–15 l/m² per session) rather than a little every day, so the roots grow deep. To see how much has landed, put an empty tuna tin in the sprinkler’s range: about 1–1.5 cm of water equals 10–15 l/m².

Case 2: Dog urine

Urine contains a lot of nitrogen and salts. At the edge it acts like fertiliser (dark green), in the centre it burns the grass. Water fresh spots immediately with a watering can. Rake out and overseed patches that are already dead.

Case 3: Grubs

Grubs are the larvae of chafer beetles and similar species, and they eat grass roots in late summer and spring. In home gardens the go-to is nematodes (Heterorhabditis), available from garden centres. They only work at soil temperatures above about 12 °C, so in late summer or late spring. Keep the soil moist before and after. Then overseed the damaged areas.

Case 4: Thatch, compaction, fungus

Dead stems and moss form a thatch layer that blocks water and air. Scarifying in spring (when the lawn is growing strongly, usually April–May) or late summer fixes it. Fungal diseases often appear with nutrient deficiency, waterlogging and leaves left lying. Potassium-rich autumn feed, clearing leaves and good aeration help prevent them.

How to repair bare patches (overseeding)

1. Rake out dead grass firmly.
2. Loosen the soil 2–3 cm deep and work in some lawn soil if needed.
3. Spread repair seed evenly (quantity per pack) and rake in lightly.
4. Firm down, e.g. with a board or by treading.
5. Keep it constantly moist for 3–4 weeks, which means a fine daily watering in dry weather. Drying out is the most common reason for failure.
6. Only mow once the new grass is about 8–10 cm tall.

Timing: Grass seed needs soil temperatures of around 10–20 °C. April–May and late August–September are ideal. In November overseeding is no longer worth it, so clear the leaves and repair in spring.

Common mistakes

• Watering briefly every day. It encourages shallow roots and moss.
• Mowing too short. Below 4 cm, lawns scorch faster in summer.
• Feeding in a heatwave. Without watering afterwards, the grass burns.
• Letting new seed dry out. A single dry day can kill the seedlings.