Question
I have a row of 45 arborvitae that came with my house...we are only there 3 years.  We created a gated pen with pea gravel for my dogs to go to the bathroom.  The ground slants downhill towards the arborvitae.  There are 10 that line the fence.  The dogs do not urinate on the arborvitaes ...girls that squat.  However this year only those 10 arborvitae and two other random ones down the line completely died.  Question is could the urine in the ground going downhill towards them have killed them overtime....also any suggestions on planting these again or other hedges as this acts as a natural fence that I really like.  Thanks!!

Answer
Dear Rose, Arborvitae are one of those tree/shrubs that prefer alkaline soil and urine is acidic.  So whether the dogs are squatting or standing, the urine makes the soil more acidic which the arborvitae doesn't like.  It may be possible to make the soil more alkaline by adding aluminum sulfate, which can be found in most garden centers, to the soil by watering it in.  That may fix your problem and would be worth a try, but since the urine flow is steady, you would have to reapply the aluminum sulfate frequently to keep neutralizing the urine.  I would try it on the remaining plants to see if it helps, but you may have to end up replacing the plants anyway.  In that case, I would go with a shrub that prefers acidic soil, which is almost everything else.  Another suggestion would be if you can place a low fence near the trees and drive in some deep edging (about 6 inches) into the soil, so there would be a barrier between the plants and the urine.  Also, when you water, water VERY deeply, as this will help to drain off the excess acidity in the soil.  Try these measures, especially the deep watering and the aluminum sulfate and you may be able to keep the rest of the plants.  Good luck, and let me know if I may be of further assistance. Melissa