Lawn urine burn

also called Dog spot

Round dead patches in the lawn with a ring of lush dark green around them. Nitrogen — too much in the middle, exactly right at the edge.

Disorder Disfiguring Doesn't spread

What you'll see

Circular brown dead patches ten to thirty centimeters across, appearing over a few days.
A ring of unusually dark, fast-growing grass around the outside of each dead spot, which is the diagnostic sign.
Damage scattered where the dog goes rather than following drainage or shade.
Worst on lawns that were dry at the time and on freshly fertilized turf.
Grass regrowing from the edges over several weeks once the salts have washed out.

Why it happens

Dog urine is concentrated nitrogen and salts. In the middle of the spot it is a massive overdose that scorches the grass exactly as a spill of fertilizer would; at the diluted edge it is a perfect feed, which is why the ring is greener than the rest of the lawn. Female dogs are blamed more often only because they empty in one place.

Dry weather, an already well-fed lawn, and a dog with a routine spot. Fine fescues and Kentucky bluegrass burn most easily; ryegrass and tall fescue take it better.

Treating it

Water the spot heavily as soon as you can — a full watering can within a few hours prevents most of the damage.
Rake out the dead grass, top-dress with a little compost and reseed the bare patch.
Water the whole lawn deeply and let the ring even out over a few weeks.
Do not add fertilizer to the area; it already has far too much nitrogen.
Ignore the supplements sold to change a dog urine — none has good evidence behind it and some are bad for the dog.

Keeping it away

Train the dog to one gravelled or mulched corner, and water that spot regularly.
Keep a watering can by the door and rinse the spot after each use.
Make sure the dog has plenty of water to drink; dilute urine does far less damage.
Feed the lawn less, so it is not already carrying the nitrogen it can use.
Overseed with tall fescue or ryegrass, which tolerate it markedly better.

Who gets it

Lawn grasses, and any low border plant that is repeatedly marked.