Tall trees at the lot line might not be the best way to get privacy. Sometimes it's better to add privacy closer to where you are standing/sitting. Less expensive and more effective.

Here's a schematic of the benefit of planting something closer to where you need the privacy. Your house, windows and deck on the left, your higher-up neighbours on the right. Sight lines in yellow. this is the most challenging scenario, where you need privacy from from eyes that are much higher than you.

We can help if you tell us more about where you live, how much light and sun your yard gets, and where you need privacy from. Pictures and measurements help a lot.

This makes sense but in our case because our lot is so small (38 ft wide) we basically sit on the lot line! Pic below of where we’re trying to add privacy. Our deck sits up high which is why we want some taller trees.

We’re in southern Wisconsin. The area is full sun from mid morning to evening. The max width in the space were looking to fill is 6.5 ft and length along the lot line is about 70 ft from the house (where our deck is) to the back lot line.

Stick with the Emerald Green ('Smaragd') arborvitaes. Green Giants grow far too wide and tall and will be dwarfing that tiny area in no time. Ditto the hybrid willows. And they provide very little in the way of privacy anyway.

Some photos. First is the view from our deck while sitting which is what we’re trying to enhance. Second is from across the driveway to where we’re looking to add privacy. Third is along the lot line from starting next to the deck. Fourth is lot line next to garage.

Agree with gardengal. Additionally, I'd add 2 pieces of 4' x 8' white lattice to the corner. Attach it to the existing railing with white zip ties. Instant privacy.

That’s a great idea! Thanks @partim!

And thanks gardengal for the tips on the arborvitae! Had no idea green giants would grow to be too big.

There are a number of fastigiate trees available these days that may work for you. I wouldn't recommend planting a long hedge row of them, but placed as needed for height with shorter narrow shrubs along the lot line can help you create a more interesting landscape in a small lot.

Trees, Shade, Columnar or Fastigiate (uaex.edu)

The feeling of privacy is different from whether or not you can be seen. My city back yard feels incredibly private and many people remark on that. I have 2 pieces of lattice in the least-private part of my yard, which makes a huge difference. We also installed an inexpensive metal gazebo on our deck, with a fabric roof that comes off in winter. It only cost about $200. We don't need the shade from the roof but what we do need is the feeling of privacy it gives us.

https://www.flowerchick.com/best-privacy-trees-and-shrubs-for-zones-5-6/

Artificial wall hedge

https://www.wayfair.com/outdoor/pdp/e-joy-15-ft-h-x-15-ft-w-artificial-wall-hedge-polyethylene-privacy-screen-w001557668.html