Oops...forgot to mention that it is in a sunny area.

They are faster than the arbs for sure but not all that fast - 6-10" per year, depending on conditions. That's generally considered a moderate rate of growth.

They are not at all as tolerant of our wet winters as are the arbs, so make sure your soil is very well draining.

Blue forms of Rocky Mountain juniper soon become unattractive (gaps in foliage with algae making older leaves look dirty) here - stick with Thuja. The 'Smaragd' is probably so popular because it is hard to beat. There is nothing that will race up but stay short like bamboo, which actually produces stems which reach their full height the first year and then never grow taller. Otherwise if you want something narrow and short (20' is nothing for a tree) without annual shearing you are pretty much stuck with having to plant more restrained growers that do not explode out of control at any point in their development. Apart from bamboo the oft desired instant living wall of fixed height does not really exist.

In fact, I want it as tall as possible to screen a big house and a road. I just don't want it as wide since I need the space for my plants. I was also thinking of laurels but I am worried about it being wide. I asked the garden hotline from the city and they suggested Leyland Cypress. Will that work? Thank you all for the great ideas.

I am attaching a picture of the fence and you can see the big house and the road. As I mentioned before, the area in front of the fence is the sunniest spot of our yard. I have an grape arbor built on the spot where the green cone is. The area between the arbor and the fence now has blueberries and raspberries. This is the view from our deck.

Leyland cypress will not fit unless you shear it, otherwise it grows very large.

I say stick with Thuja too. Can't go wrong there.
Skyrocket Juniper gets ragged looking if it grows fast. To look it's best, it needs a drier climate than ours and full sun.
Mike

Thanks, Mike

How about Green Giants? I was just reading about them and they grow faster than the Emerald Arbovitaes.

Green giants grow wide and tall without a lot of shearing. It you're up to the task of shearing them several times a year, then go for it. Sooner or later though, you will probably loose the battle. They get large, hence the name 'Giant'.
Mike

You're welcome!

Does that mean that the Emerald Arbovitae is the only one that I can plant in that area?