Sep 14, 2011 – A Spotty Problem

QUESTION:

What would make spots in a lawn a different color green, such as a bright green?

ANSWER:

My temptation is to go with one very likely cause, and that is one called Canis lupis familiaris - our common dog. Urine is high in nitrogen, and while it may cause a burned spot in that lawn initially it then provides a high nitrogen source for the turf, which begins to grow much more rapidly and healthier at the spot where the dog decided to do its business. Even a pile of poop, cleaned up and removed, may have been the source of nutrients that leached into the soil and were used by the turf for healthier growth. Where female dogs routinely use the lawn as their bathroom you will get these darker green spots all over the turf.

I recall one incident where a homeowner was blaming a pest control technician and his insecticides for "burning" plants in the garden surrounding a lawn. As we inspected these plants the front door screen was suddenly shoved open by the homeowner's dog, and the dog immediately ran across the lawn and lifted his leg on those plants, confirming my suspicion that the burned foliage had nothing to do with pest control chemicals. In your case it could even be neighboring dogs that are let out to relieve themselves at night, and choose this lawn as the best bathroom in town. Dog urine is not going to harm the lawn overall, but will cause brown spots and then these dark green spots, disrupting the otherwise smooth look to the lawn.

Other than urine, improper fertilizing can result in spotty coloring on turf, although this usually is seen as long rows of darker and lighter green areas and streaks of dead areas where excessive fertilizer may have been dumped. Nitrogen is usually the reason for the green of plants, and while it is a necessary ingredient it also can be applied too heavily, resulting in this burning of the foliage. There also can be discoloration caused by fungus problems in lawns, and the "fairy ring" effect where a fungus problem moves outward from its original spot shows as a darker ring surrounded by the lighter ring or dying turf. However, these generally are not spots as you describe, and what you see would seem much more to be the result of some nitrogen source ending up on the lawn in widespread places, much more typical of dog urine.

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