I want to plant a hedge along approximately 110 feet of existing fence for privacy. I have two dogs. Yew has been suggested but I have heard it is poisonous to dogs. Boxwoods have been suggested too but I have also been told it does not stand up well to dog urine. Recommendations? Comments?
If your intention is to plant a hedge for privacy then you probably should plant something that will grow fairly quickly and grow to a good height. Boxwood such as Littleleaf or Japanese boxwood (B. microphylla) are slow-growing shrubs and generally add less than 12 inches per year. They only reach a height of 4ft with a spread of 4ft. Furthermore, they require proper care to thrive as a vigorous shrub and grow at its expected rate. Therefore, these varieties of boxwood may not be a good choice for you. On the other hand the Common or American boxwood (B. sempervirens) grows to a height of 10 to 15 feet. It is a wide-spreading shrub or small tree with dense, evergreen foliage and certainly is worth considering.
Below are links to articles previously published by Toronto Master Gardeners on hedges which provide plant suggestions.
https://www.torontomastergardeners.ca/askagardener/hedging-for-toronto/
It would be prudent to avoid choosing the yew for your hedge because the seed inside the red fruit is indeed poisonous.
With regard to your dogs possibly using the area near the new hedge for their toilet the following articles previously published by Toronto Master Gardeners should prove useful.
https://www.torontomastergardeners.ca/askagardener/dog-friendly-plants/
https://www.torontomastergardeners.ca/askagardener/dog-urine-on-cedar-bushes/