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Yellow Spots on a Green Lawn


Dog urine spots of yellowed grass are often surrounded by a ring of denser green living grass caused by a slightly lower concentration of nitrogen.

Dog owners, especially owners of female dogs, know the problem. Their grass is dotted with yellow spots 4 to 8 inches (10 to 20 cm) in diameter caused by dog urine. It’s especially a problem with female dogs since they squat to urinate, pouring the liquid directly onto the lawn, but some males also squat to urinate, especially when on their home turf (otherwise, they tend to urinate on upright objects in order to mark their passage and thus less urine lands on the grass).

Small dogs are less of a problem than large ones.

It goes without saying that large dogs produce more urine and therefore larger and more visible spots, while the urine of small dogs can be less damaging because there is simply less of it… unless they are forced to use a limited area of lawn.

The Cause

Curiously, the main cause of these dog spots is nitrogen from the ammonia urine contains, the same mineral we apply to lawns to boost their growth. But as much as nitrogen can stimulate growth in the right quantities, too much of it can damage or kill plants. Note too that when the soil is moist, as is usually the case in the spring, dog urine actually does make the grass grow faster, leading to clumps of darker green grass. It’s when the soil is on the dry side and therefore the urine isn’t diluted that yellow spots occur. Often there will be a band of greener grass all around the yellow patch, because the urine is diluted enough as it spans out on the margins of the spot to stimulate grass growth rather than kill it.


Train your dog to use a dog potty corner.

The best treatment for dog urine spots in a lawn is to install a dog potty corner where there is no vegetation: it could be covered in pea gravel, sand, or mulch. Of course, you’ll have to train your dog to use it.

The second best way is to always be around when your dog urinates, then you can immediately irrigate the spot with a good spray of water, as the water will dilute the nitrogen to an acceptable level. It isn’t necessary or even desirable to add any products to the water, or use a special kind of water: plain tap water is all you need.

Another tip: keeping the lawn at least slightly moist at all times will also help to dilute the nitrogen and prevent damage. It’s dry lawns that suffer the most. And regular fertilization with a nitrogen-rich fertilizer will make the lawn greener overall, helping mask the dark green spots that show up early in the season.

No Need For Special Products

When you start searching on the Internet, you will find lots of sites that promote homemade or commercial treatments (baking powder, soap dish, gypsum, etc.) to “neutralize” dog urine, but these products are no more effective than water alone and can sometimes even be harmful. Often these treatments are said to work by lowering the alkaline pH of urine. But dog urine is not normally alkaline, but is rather slightly acidic, with a pH of about 6.0 to 6.5: just about right for healthy lawn growth. Why apply a product to reduce alkaline conditions when that isn’t the problem? Gypsum or baking powder won’t “neutralize” excess nitrogen!

Note that most of these treatments conclude by recommending a good soaking with water. Try water without using the product and you’ll see the water treatment is just as effective.

Lawn Repairs

Sometimes if the sod is only slightly yellowed, a thorough watering can save it. But if there are no signs of it greening up a week after watering, the patch is definitely dead.

If so, remove the dead sod, rake the earth, add a thin layer (1/2 to 1 inch/1-2 cm) of good soil, then resow with quality lawn seed. Keep the location moist for the next 2 weeks to allow the seedlings to fill in. Repairs are most effective when the temperatures are cool.

When nothing else works …

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Your lawn is still dotted with yellow spots despite your best efforts? You can always spray paint the yellow patches green! No, that is not a joke: you can buy lawn paint specifically designed to cover up any kind of damage to lawns. Desperate situations call for desperate measures, I suppose!

Or learn to live with a less than perfect lawn. After all, there are other more important things in life that green grass!20160715E

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