I live in Toronto at StClair and Bathurst area. I think the soil type is clay. I have a 25ft long x 6ft high fence on my backyard. My backyard gets sunlight from noon until close to sunset. Along the fence and as close as possible to the fence, I want to have trees/plants with minimum spread (I have only 1ft space for 12ft length of fence between the fence and walkout stairs wall. For the rest of the fence length I have 2.5ft of space in from the fence). I also want a height of 14-16ft. In my search, I saw cedar hedge may be option, but it needs at least 3ft from the fence to plant and its spread is 3 to 4ft. Also, I do not want to put any vines or similar shrubs as they attract bees and other insects.
Attached sketch may be more descriptive.
Could you please help me if there are other options?
Your privacy dilemma is common to many city dwellers in downtown Toronto. Your need for privacy over top of the 6 foot height of your fence is also challenging. For the very narrow 12-foot space, you may wish to consider a series of tall narrow planters that are available at home and garden centres this summer. Planting these with a tall grass, or a small evergreen, or even some of the topiary-style tropical shrubs available at nurseries in the summer will give you a repeated design with enough height to draw the eye. In this very narrow space, unless you wish to plant vines, you are not likely to find hedging narrow enough at maturity to be practical. If you decide that planters may work for you, knowledgeable staff at any of the large Toronto/GTA area nurseries could help you with plant selection. Keep in mind that these container plantings may need to be replaced every year, depending upon the winter hardiness of the plants you choose.
For the rest of the fence length, you have a little more choice in terms of hedging plants, although as you have already discovered, trees that grow as tall as 14 to 16 feet also tend to be wider at their base. DeGroot’s Spire cedar or Skyrocket juniper are two options with a compact, narrow pyramidal form that you might consider, although they will only approach 10 to 12 feet at maturity.
The Toronto Master Gardeners has answered a couple of questions on this subject previously, and these posts might give you some ideas. For a privacy screen in a small space: https://www.torontomastergardeners.ca/askagardener/trees-for-privacy-in-a-small-space/ and for suggestions for tall narrow plants for hedging: https://www.torontomastergardeners.ca/askagardener/hedging-for-toronto/
Vines are not your preference, but one of their advantages is that by adding a section of trellising to the top of your fence, they can add height without taking up much space at ground level. If you would like to read more, here is a link that discusses more ideas for privacy, including vines.
Finally, there is the option of deciduous tree hedging in which the lower branches are removed as the tree grows to create its canopy above the top of the fence. These hedges would typically need to be pruned to maintain their shape (and to avoid encroaching on your neighbour’s property if this is an issue). Here is another Toronto Master Gardeners post on the subject of “pleached” hedging, the art of “limbing up” hedging trees so that they seem to float above the ground, leaving space at ground level but providing privacy above: https://www.torontomastergardeners.ca/askagardener/hornbeam-hedging/ Beautiful, but obviously a more challenging project!