Now where did we leave off last time? Oh yes I was talking about plants being too close to the house causing heat and drought damage to the plant. Well while we’re evaluating distance let’s also talk about backyard fences. There are several perspectives to play out. First of all, be a good neighbour. Don’t plant something that your neighbour doesn’t want hanging over their yard. If your neighbour benefits from shade and doesn’t mind doing a little pruning they may like your tree shading their backyard. After all they don’t have to look after your tree and still get some privacy and shade benefits.
On the flip side if they are trying to grow a veggie garden and you shade them out, that’s not really being a good neighbour and we all need to be good Neighbors.
The second consideration is the fence footing and impact of large roots. This is much more problematic with the very large trees, again, I would simply suggest not planting cottonwoods and poplars near a fence. They will be very large and the roots can push around the posts of the fence. If you insist on planting a large tree near a fence line I would recommend being at least 20 ft. away, preferably further. You can plant trees near fence as long as they are trimmed up above the fence once they’re larger. In this case the width of your lawn mower may dictate how far away from the fence you want to be. Even if you plant the tree in wood chips or soil you will need working space and you don’t want an odd-looking tree trimmed disproportionately against the fence. Here too you still want to choose plants that will not be invading your neighbor’s yard. The best small trees for this would be Ming cherry, they are seedless and won’t drop anything either. Other narrow and smaller sized trees are best, here is a short list; any of the columnar Flowering Crabapples, columnar Cedars, and Parkland Pillar Birch, these are usually not more than 5 to 7 feet in width but can be 15 to 30 ft. tall depending on which selection.
On a side note the Cedars and birch do much better on east and north sides of a fence because their roots stay cooler and moist. Columnar crab apples can grow anywhere but tolerate the heat much better than the other two. Courageous, Gladiator, Starlight Flowering crabapples and some spruce are only slightly broader at about 12 to 15 ft. wide. I also recommend the small non-aggressive tree list near the beginning of this conversation as good options again.
Last side point would be to strategically place trees based on Neighbors decks or windows that you would prefer to have privacy from or a deck or window you would prefer to have the most privacy for. Remember even good neighbours enjoy some privacy. It might actually be part of what makes them good neighbour’s.