It's not unreasonable for a homeowner who puts a good deal of money, time and energy into maintaining a lovely lawn to put up a sign warning dog walkers to "keep off the grass." Brown patches on lawns are evidence that one or more dogs have a favourite bathroom spot. Low-lying plant leaves or shrubs with browning edges might be the victim of a male dog's leg lift.
Dog Urine Can Damage or Kill Plants and Grass
Plants and grass are susceptible to damage from dog urine because of its chemical composition. According to a publication provided by the University of Nebraska, Lincoln, the salts in dog urine are very damaging to plants. You can see the effect most commonly on lawns, which are the most noticeable victim of dog urine spotting. Brown spots and darker green areas are the effects of a dog urinating on the lawn. Similarly, leaves will brown out on low-lying plants if dogs urinate on them too often.
Male versus Female Dogs
Despite some urban legends to the contrary, the chemical composition of the urine is the same whether the dog is male or female. There is a greater damaging effect on the plants dogs pee on, however, from dogs who squat when they urinate versus those who lift their leg. This is due to the large volume of urine they deposit in concentrated areas. Most dogs who squat when they pee are female, but some males do, too, especially if they are feeble or in the confines of their own yard.
Squatting versus Marking
It's the squatting that matters. Marking, on the other hand, is a purely male dog thing. Male dogs have a tendency to urinate or "mark" vertical objects in the landscape, such as lampposts and fire hydrants, but also including trees, shrubs and other plants. The amount of urine deposited when a male dog marks in this way, however, is usually quite small. Therefore, a male dog's urine marking, while possibly troublesome, is much less of a problem than a male dog who squats to urinate on low-lying plants, grass or ground cover.
Damaging Effects of Salts and Nitrogen
The reason dog urine can kill plants is its chemical composition. Contrary to common belief, dog urine does not cause spotting or browning because it is alkaline. Rather, dog urine kills greenery due to its high concentration of nitrogen and salts, which overwhelm a small patch of plantings or grass and cause plant "burn" similar to the browning and killing effect of over-fertilisation. Brown spots appear in lawns or on leaves. If the nitrogen does not overwhelm the area, it can simply darken the green of plants and grass, actually making the area grow faster.
According to specialists, the best ways to protect plants or grass from an overdose of nitrogen and salt in dog urine is to immediately douse the area with water after a dog urinates. Flushing the area will wash the nitrogen and salts into surrounding ground, causing a neutralising and dilution effect. Using a hose to wash away dog urine on plants will help prevent their leaves from browning.
- University of Nebraska Lincoln: IPM for Trees and Shrubs on School Grounds
- Colorado State University Extension: Dog Urine Damage on Lawns: Causes, Cures and Prevention
- Improve Your Garden Soil: Avoiding Fertilizer Burn
- University of California Division of Agriculture and Natural Resources: Lawns 'N' Dogs
- University of Minnesota Extension Service: Out Spot! Out? Debunking Dog Blight Myths