This living screen of Ficus retusis ssp nitida is only about 18 inches (~50 cm) wide, but at least 15 feet (5 m) tall:
Here's another example of a tall, narrow screening hedge. It is highly successful in terms of screening--you can't see through it at any point. Someone wanted their privacy from the neighbors above, and they got it. No maintenance--probably not. This screen appears to be sheared regularly. The uniformity and density of the screen is appealing.
It consists of about 100 Ficus retusis ssp nitida or Ficus benjamina--I have not been able to tell them apart lately--planted closely together. The base shows how closely:
The success of the screening must be attributed to care in both planting and maintenance. This hedge is planted at the top of a very steep slope. The root system of the hedge is supported by a small retaining wall, to allow for extra root space. There is a drip system for watering the hedge that is functional and maintained. Regular shearing encourages and maintains dense foliage.
These homeowners were serious about having a screen, and they made the effort to do it right. My sole reservation about this effective screen is that it screams, "I'm a privacy screen! I'm a privacy screen!"
Tall and dense:
Again, we see that maintenance matters.